diff --git a/src/ActionsGridFieldItemRequest.php b/src/ActionsGridFieldItemRequest.php
index 381ae4b..bfd3dd1 100644
--- a/src/ActionsGridFieldItemRequest.php
+++ b/src/ActionsGridFieldItemRequest.php
@@ -9,9 +9,11 @@
 use SilverStripe\ORM\DataObject;
 use SilverStripe\Core\Extensible;
 use SilverStripe\Forms\FieldList;
+use SilverStripe\Forms\FormField;
 use SilverStripe\Control\Director;
 use SilverStripe\Forms\FormAction;
 use SilverStripe\Admin\LeftAndMain;
+use SilverStripe\Forms\HiddenField;
 use SilverStripe\ORM\DataExtension;
 use SilverStripe\Control\Controller;
 use SilverStripe\Control\HTTPRequest;
@@ -23,7 +25,6 @@
 use SilverStripe\ORM\FieldType\DBHTMLText;
 use SilverStripe\Control\HTTPResponse_Exception;
 use SilverStripe\Forms\GridField\GridFieldDetailForm_ItemRequest;
-use SilverStripe\Forms\HiddenField;
 
 /**
  * Decorates GridDetailForm_ItemRequest to use new form actions and buttons.
@@ -36,7 +37,7 @@
  *
  * @link https://github.com/unclecheese/silverstripe-gridfield-betterbuttons
  * @link https://github.com/unclecheese/silverstripe-gridfield-betterbuttons/blob/master/src/Extensions/GridFieldBetterButtonsItemRequest.php
- * @property LeftAndMain|GridFieldDetailForm_ItemRequest|ActionsGridFieldItemRequest $owner
+ * @property LeftAndMain&GridFieldDetailForm_ItemRequest&ActionsGridFieldItemRequest $owner
  */
 class ActionsGridFieldItemRequest extends DataExtension
 {
@@ -68,7 +69,7 @@ class ActionsGridFieldItemRequest extends DataExtension
     private static $enable_utils_prev_next = false;
 
     /**
-     * @var array Allowed controller actions
+     * @var array<string> Allowed controller actions
      */
     private static $allowed_actions = [
         'doSaveAndClose',
@@ -79,7 +80,8 @@ class ActionsGridFieldItemRequest extends DataExtension
     ];
 
     /**
-     * @return array
+     * @param FieldList $actions
+     * @return array<string>
      */
     protected function getAvailableActions($actions)
     {
@@ -116,6 +118,8 @@ public function updateEditForm(Form $form)
      * GridField_ItemRequest defines its own set of actions so we need to add ours
      * We add our custom save&close, save&next and other tweaks
      * Actions can be made readonly after this extension point
+     * @param FieldList $actions
+     * @return void
      */
     public function updateFormActions($actions)
     {
@@ -201,8 +205,10 @@ public function updateFormActions($actions)
     protected function processDropUpMenu($actions)
     {
         // The Drop-up container may already exist
+        /** @var ?Tab $dropUpContainer */
         $dropUpContainer = $actions->fieldByName('ActionMenus.MoreOptions');
         foreach ($actions as $action) {
+            //@phpstan-ignore-next-line
             if ($action->hasMethod('getDropUp') && $action->getDropUp()) {
                 if (!$dropUpContainer) {
                     $dropUpContainer = $this->createDropUpContainer($actions);
@@ -271,6 +277,7 @@ public function moveCancelAndDelete(FieldList $actions, DataObject $record)
             }
             // Set custom title
             if ($record->hasMethod('getDeleteButtonTitle')) {
+                //@phpstan-ignore-next-line
                 $deleteAction->setTitle($record->getDeleteButtonTitle());
             }
         }
@@ -286,6 +293,7 @@ public function moveCancelAndDelete(FieldList $actions, DataObject $record)
             }
             // Set custom titlte
             if ($record->hasMethod('getCancelButtonTitle')) {
+                //@phpstan-ignore-next-line
                 $cancelButton->setTitle($record->getCancelButtonTitle());
             }
         }
@@ -299,6 +307,7 @@ public function getCustomPreviousRecordID(DataObject $record)
     {
         // This will overwrite state provided record
         if (self::config()->enable_custom_prevnext && $record->hasMethod('PrevRecord')) {
+            //@phpstan-ignore-next-line
             return $record->PrevRecord()->ID ?? 0;
         }
         return $this->owner->getPreviousRecordID();
@@ -313,11 +322,28 @@ public function getCustomNextRecordID(DataObject $record)
 
         // This will overwrite state provided record
         if (self::config()->enable_custom_prevnext && $record->hasMethod('NextRecord')) {
+            //@phpstan-ignore-next-line
             return $record->NextRecord()->ID ?? 0;
         }
         return $this->owner->getNextRecordID();
     }
 
+    /**
+     * @param FieldList $actions
+     * @return CompositeField|FieldList
+     */
+    protected function getMajorActions(FieldList $actions)
+    {
+        /** @var ?CompositeField $MajorActions */
+        $MajorActions = $actions->fieldByName('MajorActions');
+
+        // If it doesn't exist, push to default group
+        if (!$MajorActions) {
+            $MajorActions = $actions;
+        }
+        return $MajorActions;
+    }
+
     /**
      * @param FieldList $actions
      * @param DataObject $record
@@ -329,12 +355,7 @@ public function addSaveNextAndPrevious(FieldList $actions, DataObject $record)
             return;
         }
 
-        $MajorActions = $actions->fieldByName('MajorActions');
-
-        // If it doesn't exist, push to default group
-        if (!$MajorActions) {
-            $MajorActions = $actions;
-        }
+        $MajorActions = $this->getMajorActions($actions);
 
         // TODO: state is having a hard time on post
         // @link https://github.com/silverstripe/silverstripe-framework/issues/10742
@@ -384,12 +405,7 @@ public function addSaveAndClose(FieldList $actions, DataObject $record)
             return;
         }
 
-        $MajorActions = $actions->fieldByName('MajorActions');
-
-        // If it doesn't exist, push to default group
-        if (!$MajorActions) {
-            $MajorActions = $actions;
-        }
+        $MajorActions = $this->getMajorActions($actions);
 
         if ($record->ID) {
             $label = _t('ActionsGridFieldItemRequest.SAVEANDCLOSE', 'Save and Close');
@@ -419,13 +435,12 @@ protected function getBtnClassForRecord(DataObject $record)
         if ($record->ID) {
             return 'btn-outline-primary';
         }
-
         return 'btn-primary';
     }
 
     /**
-     * @param $action
-     * @param $definedActions
+     * @param string $action
+     * @param array<FormField>|FieldList $definedActions
      * @return mixed|CompositeField|null
      */
     protected static function findAction($action, $definedActions)
@@ -443,6 +458,7 @@ protected static function findAction($action, $definedActions)
             $definedActionName = $definedAction->getName();
 
             if ($definedAction->hasMethod('actionName')) {
+                //@phpstan-ignore-next-line
                 $definedActionName = $definedAction->actionName();
             }
             if ($definedActionName === $action) {
@@ -460,7 +476,7 @@ protected static function findAction($action, $definedActions)
      * Action must be declared in getCMSActions to be called
      *
      * @param string $action
-     * @param array $data
+     * @param array<string,mixed> $data
      * @param Form $form
      * @return HTTPResponse|DBHTMLText|string
      * @throws HTTPResponse_Exception
@@ -480,6 +496,7 @@ protected function forwardActionToRecord($action, $data = [], $form = null)
         } elseif (!empty($data['ClassName']) && !empty($data['ID'])) {
             $record = DataObject::get_by_id($data['ClassName'], $data['ID']);
         } elseif ($controller->hasMethod("getRecord")) {
+            //@phpstan-ignore-next-line
             $record = $controller->getRecord();
         }
 
@@ -533,6 +550,7 @@ protected function forwardActionToRecord($action, $data = [], $form = null)
                 $message = $result;
             }
         } catch (Exception $ex) {
+            $result = null;
             $error = true;
             $message = $ex->getMessage();
         }
@@ -551,11 +569,16 @@ protected function forwardActionToRecord($action, $data = [], $form = null)
         }
 
         // Progressive actions return array with json data
+        //@phpstan-ignore-next-line
         if (method_exists($clickedAction, 'getProgressive') && $clickedAction->getProgressive()) {
             $response = $controller->getResponse();
             $response->addHeader('Content-Type', 'application/json');
             if ($result) {
-                $response->setBody(json_encode($result));
+                $encodedResult = json_encode($result);
+                if (!$encodedResult) {
+                    $encodedResult = json_last_error_msg();
+                }
+                $response->setBody($encodedResult);
             }
 
             return $response;
@@ -572,6 +595,7 @@ protected function forwardActionToRecord($action, $data = [], $form = null)
 
         if (Director::is_ajax()) {
             $controller->getResponse()->addHeader('X-Status', rawurlencode($message));
+            //@phpstan-ignore-next-line
             if (method_exists($clickedAction, 'getShouldRefresh') && $clickedAction->getShouldRefresh()) {
                 $controller->getResponse()->addHeader('X-Reload', "true");
             }
@@ -582,6 +606,7 @@ protected function forwardActionToRecord($action, $data = [], $form = null)
         } else {
             // If the controller support sessionMessage, use it instead of form
             if ($controller->hasMethod('sessionMessage')) {
+                //@phpstan-ignore-next-line
                 $controller->sessionMessage($message, $status, ValidationResult::CAST_HTML);
             } else {
                 $form->sessionMessage($message, $status, ValidationResult::CAST_HTML);
@@ -589,8 +614,10 @@ protected function forwardActionToRecord($action, $data = [], $form = null)
         }
 
         // Custom redirect
+        //@phpstan-ignore-next-line
         if (method_exists($clickedAction, 'getRedirectURL') && $clickedAction->getRedirectURL()) {
             $controller->getResponse()->addHeader('X-Reload', "true"); // we probably need a full ui refresh
+            //@phpstan-ignore-next-line
             return $controller->redirect($clickedAction->getRedirectURL());
         }
 
@@ -628,7 +655,7 @@ public function doCustomLink(HTTPRequest $request)
      *   [doTestAction] => 1
      * )
      *
-     * @param array $data The form data
+     * @param array<string,mixed> $data The form data
      * @param Form $form The form object
      * @return HTTPResponse|DBHTMLText|string
      * @throws Exception
@@ -636,15 +663,15 @@ public function doCustomLink(HTTPRequest $request)
     public function doCustomAction($data, $form)
     {
         $action = key($data['action_doCustomAction']);
-
         return $this->forwardActionToRecord($action, $data, $form);
     }
 
     /**
      * Saves the form and goes back to list view
      *
-     * @param array $data The form data
+     * @param array<string,mixed> $data The form data
      * @param Form $form The form object
+     * @return HTTPResponse
      */
     public function doSaveAndClose($data, $form)
     {
@@ -666,8 +693,9 @@ public function doSaveAndClose($data, $form)
     /**
      * Saves the form and goes back to the next item
      *
-     * @param array $data The form data
+     * @param array<string,mixed> $data The form data
      * @param Form $form The form object
+     * @return HTTPResponse
      */
     public function doSaveAndNext($data, $form)
     {
@@ -680,6 +708,10 @@ public function doSaveAndNext($data, $form)
         $class = get_class($record);
         $getNextRecordID = $data['_cmsactions']['next'][$class] ?? $this->getCustomNextRecordID($record);
         $class = get_class($record);
+        if (!$class) {
+            throw new Exception("Could not get class");
+        }
+        /** @var ?DataObject $next */
         $next = $class::get()->byID($getNextRecordID);
 
         $link = $this->owner->getEditLink($getNextRecordID);
@@ -699,8 +731,9 @@ public function doSaveAndNext($data, $form)
     /**
      * Saves the form and goes to the previous item
      *
-     * @param array $data The form data
+     * @param array<string,mixed> $data The form data
      * @param Form $form The form object
+     * @return HTTPResponse
      */
     public function doSaveAndPrev($data, $form)
     {
@@ -711,8 +744,13 @@ public function doSaveAndPrev($data, $form)
         $controller->getResponse()->addHeader("X-Pjax", "Content");
 
         $class = get_class($record);
-        $getPreviousRecordID = $data['_cmsactions']['prev'][$class] ?? $this->getPreviousRecordID($record);
+        $getPreviousRecordID = $data['_cmsactions']['prev'][$class] ?? $this->getCustomPreviousRecordID($record);
         $class = get_class($record);
+        if (!$class) {
+            throw new Exception("Could not get class");
+        }
+
+        /** @var ?DataObject $prev */
         $prev = $class::get()->byID($getPreviousRecordID);
 
         $link = $this->owner->getEditLink($getPreviousRecordID);
@@ -729,6 +767,11 @@ public function doSaveAndPrev($data, $form)
         return $controller->redirect($link);
     }
 
+    /**
+     * @param string $url
+     * @param array<mixed> $data
+     * @return string
+     */
     protected function addGridState($url, $data)
     {
         // This should not be necessary at all if the state is correctly passed along
@@ -766,6 +809,10 @@ protected function getToplevelController()
         return $controller;
     }
 
+    /**
+     * @param Controller $controller
+     * @return boolean
+     */
     protected function isLeftAndMain($controller)
     {
         return is_subclass_of($controller, LeftAndMain::class);
@@ -775,8 +822,6 @@ protected function isLeftAndMain($controller)
      * Gets the back link
      *
      * @return string
-     * @todo This had to be directly copied from {@link GridFieldDetailForm_ItemRequest}
-     * because it is a protected method and not visible to a decorator!
      */
     public function getBackLink()
     {
@@ -784,6 +829,7 @@ public function getBackLink()
         $toplevelController = $this->getToplevelController();
         // Check for LeftAndMain and alike controllers with a Backlink or Breadcrumbs methods
         if ($toplevelController->hasMethod('Backlink')) {
+            //@phpstan-ignore-next-line
             $backlink = $toplevelController->Backlink();
         } elseif ($this->owner->getController()->hasMethod('Breadcrumbs')) {
             $parents = $this->owner->getController()->Breadcrumbs(false)->items;
@@ -827,6 +873,9 @@ protected function redirectAfterAction($isNewRecord, $record = null)
         // Changes to the record properties might've excluded the record from
         // a filtered list, so return back to the main view if it can't be found
         $noActionURL = $url = $controller->getRequest()->getURL();
+        if (!$url) {
+            $url = '';
+        }
 
         // The controller may not have these
         if ($controller->hasMethod('getAction')) {
@@ -840,12 +889,13 @@ protected function redirectAfterAction($isNewRecord, $record = null)
             }
         } else {
             // Simple fallback (last index of)
-            $pos = strrpos($url ?? '', 'ItemEditForm');
-            $noActionURL = substr($url ?? '', 0, $pos);
+            $pos = strrpos($url, 'ItemEditForm');
+            if (is_int($pos)) {
+                $noActionURL = substr($url, 0, $pos);
+            }
         }
 
         $controller->getRequest()->addHeader('X-Pjax', 'Content');
-
         return $controller->redirect($noActionURL, 302);
     }
 }
diff --git a/src/CmsInlineFormAction.php b/src/CmsInlineFormAction.php
index 5db1a53..ff6859e 100644
--- a/src/CmsInlineFormAction.php
+++ b/src/CmsInlineFormAction.php
@@ -19,13 +19,13 @@ class CmsInlineFormAction extends LiteralField
     use ProgressiveAction;
 
     /**
-     * @var array
+     * @var array<mixed>
      */
     protected $params = [];
 
 
     /**
-     * @var string
+     * @var string|null
      */
     protected $buttonIcon = null;
 
@@ -50,9 +50,9 @@ class CmsInlineFormAction extends LiteralField
 
     /**
      * Create a new action button.
-     * @param action $action The method to call when the button is clicked
-     * @param title $title The label on the button
-     * @param extraClass $extraClass A CSS class to apply to the button in addition to 'action'
+     * @param string $action The method to call when the button is clicked
+     * @param string $title The label on the button
+     * @param string $extraClass A CSS class to apply to the button in addition to 'action'
      */
     public function __construct($action, $title = "", $extraClass = 'btn-primary')
     {
@@ -60,11 +60,17 @@ public function __construct($action, $title = "", $extraClass = 'btn-primary')
         $this->addExtraClass($extraClass);
     }
 
+    /**
+     * @return FormField
+     */
     public function performReadonlyTransformation()
     {
         return $this->castedCopy(self::class);
     }
 
+    /**
+     * @return string
+     */
     public function getLink()
     {
         if (!$this->link) {
@@ -77,7 +83,7 @@ public function getLink()
     /**
      * Get an icon for this button
      *
-     * @return string
+     * @return string|null
      */
     public function getButtonIcon()
     {
@@ -89,13 +95,12 @@ public function getButtonIcon()
      *
      * Feel free to use SilverStripeIcons constants
      *
-     * @param string $buttonIcon An icon for this button
+     * @param string|null $buttonIcon An icon for this button
      * @return $this
      */
-    public function setButtonIcon(string $buttonIcon)
+    public function setButtonIcon(string $buttonIcon = null)
     {
         $this->buttonIcon = $buttonIcon;
-
         return $this;
     }
 
@@ -108,7 +113,7 @@ public function Type()
     }
 
     /**
-     * @param $properties
+     * @param array<string,mixed> $properties
      * @return FormField|string
      */
     public function FieldHolder($properties = [])
@@ -158,7 +163,7 @@ public function FieldHolder($properties = [])
     /**
      * Get the value of params
      *
-     * @return  array
+     * @return array<mixed>
      */
     public function getParams()
     {
@@ -168,8 +173,7 @@ public function getParams()
     /**
      * Set the value of params
      *
-     * @param array $params
-     *
+     * @param array<mixed> $params
      * @return $this
      */
     public function setParams(array $params)
@@ -214,8 +218,6 @@ public function getSubmitSelector()
     /**
      * Set the value of {@see self::$submitSelector}
      *
-     * Includes
-     *
      * @param string $selector
      * @return $this
      */
diff --git a/src/CustomAction.php b/src/CustomAction.php
index be7b437..8933475 100644
--- a/src/CustomAction.php
+++ b/src/CustomAction.php
@@ -4,6 +4,7 @@
 
 use SilverStripe\Core\Convert;
 use SilverStripe\Forms\FormAction;
+use SilverStripe\ORM\FieldType\DBHTMLText;
 
 /**
  * Custom actions to use in getCMSActions
@@ -51,9 +52,16 @@ public function Type()
         return 'action';
     }
 
+    /**
+     * @param array<string,mixed> $properties
+     * @return DBHTMLText
+     */
     public function Field($properties = [])
     {
-        $icon = $this->buttonIcon ?? $this->icon;
+        $icon = $this->buttonIcon;
+        if (!$icon) {
+            $icon = $this->icon;
+        }
         if ($icon) {
             $this->addExtraClass('font-icon');
             $this->addExtraClass('font-icon-' . $icon);
diff --git a/src/CustomButton.php b/src/CustomButton.php
index 9b5be8d..d79bf61 100644
--- a/src/CustomButton.php
+++ b/src/CustomButton.php
@@ -26,7 +26,7 @@ trait CustomButton
 
     /**
      * An icon for this button
-     * @var string
+     * @var string|null
      */
     protected $buttonIcon;
 
diff --git a/src/CustomGridField_FormAction.php b/src/CustomGridField_FormAction.php
index ceef3bc..8a808a7 100644
--- a/src/CustomGridField_FormAction.php
+++ b/src/CustomGridField_FormAction.php
@@ -8,12 +8,14 @@ class CustomGridField_FormAction extends GridField_FormAction
 {
     use ProgressiveAction;
 
+    /**
+     * @return string
+     */
     public function Type()
     {
         if ($this->progressive) {
             return 'progressive-action';
         }
-
         return 'action';
     }
 }
diff --git a/src/CustomLink.php b/src/CustomLink.php
index 54618fc..8c98c40 100644
--- a/src/CustomLink.php
+++ b/src/CustomLink.php
@@ -25,7 +25,7 @@ class CustomLink extends LiteralField
     /**
      * @param string $name
      * @param string $title
-     * @param string|array $link Will default to name of link on current record if not set
+     * @param string|array<mixed> $link Will default to name of link on current record if not set
      */
     public function __construct($name, $title = null, $link = null)
     {
@@ -41,6 +41,7 @@ public function __construct($name, $title = null, $link = null)
         if ($link && is_string($link)) {
             $this->link = $link;
         } else {
+            //@phpstan-ignore-next-line
             $this->link = $this->getModelLink($name, $link);
         }
     }
@@ -58,7 +59,7 @@ public function Type()
     }
 
     /**
-     * @param array $properties
+     * @param array<string,mixed> $properties
      * @return FormField|string
      */
     public function FieldHolder($properties = [])
@@ -84,7 +85,9 @@ public function FieldHolder($properties = [])
             $attrs[] = 'target="_blank"';
         }
         if ($this->confirmation) {
-            $attrs[] = sprintf('data-message="%s"', Convert::raw2htmlatt($this->confirmation));
+            /** @var string $att */
+            $att = Convert::raw2htmlatt($this->confirmation);
+            $attrs[] = sprintf('data-message="%s"', $att);
             if ($this->progressive) {
                 $classes[] = "confirm";
             } else {
diff --git a/src/DefaultLink.php b/src/DefaultLink.php
index c51bc96..6066eea 100644
--- a/src/DefaultLink.php
+++ b/src/DefaultLink.php
@@ -28,7 +28,7 @@ trait DefaultLink
      * If you want to call actions on the controller (ModelAdmin), use getControllerLink
      *
      * @param string $action
-     * @param array $params
+     * @param array<mixed>|null $params
      * @return string
      */
     public function getModelLink($action, array $params = null)
diff --git a/src/GridFieldRowButton.php b/src/GridFieldRowButton.php
index ed2c071..807e429 100644
--- a/src/GridFieldRowButton.php
+++ b/src/GridFieldRowButton.php
@@ -80,9 +80,9 @@ abstract public function getButtonLabel(GridField $gridField, $record, $columnNa
 
     /**
      * @param GridField $gridField
-     * @param $actionName
-     * @param $arguments
-     * @param $data
+     * @param string $actionName
+     * @param array<mixed> $arguments
+     * @param array<mixed> $data
      * @return mixed
      */
     abstract public function doHandle(GridField $gridField, $actionName, $arguments, $data);
@@ -100,7 +100,8 @@ public function getActionName()
 
     /**
      * @param GridField $gridField
-     * @param array $columns
+     * @param array<string> $columns
+     * @return void
      */
     public function augmentColumns($gridField, &$columns)
     {
@@ -115,7 +116,7 @@ public function augmentColumns($gridField, &$columns)
      * @param GridField $gridField
      * @param DataObject $record
      * @param string $columnName
-     * @return array
+     * @return array<string,string>
      */
     public function getColumnAttributes($gridField, $record, $columnName)
     {
@@ -128,7 +129,7 @@ public function getColumnAttributes($gridField, $record, $columnName)
      *
      * @param GridField $gridField
      * @param string $columnName
-     * @return array
+     * @return array<string,string>
      */
     public function getColumnMetadata($gridField, $columnName)
     {
@@ -144,7 +145,7 @@ public function getColumnMetadata($gridField, $columnName)
      * Which columns are handled by this component
      *
      * @param GridField $gridField
-     * @return array
+     * @return array<string>
      */
     public function getColumnsHandled($gridField)
     {
@@ -155,7 +156,7 @@ public function getColumnsHandled($gridField)
      * Which GridField actions are this component handling
      *
      * @param GridField $gridField
-     * @return array
+     * @return array<string>
      */
     public function getActions($gridField)
     {
@@ -208,7 +209,7 @@ public function getColumnContent($gridField, $record, $columnName)
      * @param GridField $gridField
      * @param string $actionName
      * @param mixed $arguments
-     * @param array $data - form data
+     * @param array<string,mixed> $data - form data
      * @return HTTPResponse|void
      */
     public function handleAction(GridField $gridField, $actionName, $arguments, $data)
diff --git a/src/GridFieldRowLink.php b/src/GridFieldRowLink.php
index 7d421a1..43da7a4 100644
--- a/src/GridFieldRowLink.php
+++ b/src/GridFieldRowLink.php
@@ -19,7 +19,7 @@ class GridFieldRowLink implements GridField_ColumnProvider
     /**
      * HTML classes to be added to GridField buttons
      *
-     * @var string[]
+     * @var array<string,mixed>
      */
     protected $extraClass = [
         'grid-field__icon-action--hidden-on-hover' => true,
@@ -57,7 +57,8 @@ public function __construct($name, $title, $icon = 'white-question')
      * Add a column 'Actions'
      *
      * @param GridField $gridField
-     * @param array $columns
+     * @param array<string> $columns
+     * @return void
      */
     public function augmentColumns($gridField, &$columns)
     {
@@ -72,7 +73,7 @@ public function augmentColumns($gridField, &$columns)
      * @param GridField $gridField
      * @param DataObject $record
      * @param string $columnName
-     * @return array
+     * @return array<string,string>
      */
     public function getColumnAttributes($gridField, $record, $columnName)
     {
@@ -84,7 +85,7 @@ public function getColumnAttributes($gridField, $record, $columnName)
      *
      * @param GridField $gridField
      * @param string $columnName
-     * @return array
+     * @return array<string|int,string|null>
      */
     public function getColumnMetadata($gridField, $columnName)
     {
@@ -99,7 +100,7 @@ public function getColumnMetadata($gridField, $columnName)
      * Which columns are handled by this component
      *
      * @param GridField $gridField
-     * @return array
+     * @return array<string>
      */
     public function getColumnsHandled($gridField)
     {
@@ -131,10 +132,11 @@ public function getColumnContent($gridField, $record, $columnName)
 
         $data = new ArrayData(
             [
-            'Link' => $this->getLink($gridField, $record, $columnName),
-            'ExtraClass' => $this->getExtraClass(),
-            'Title' => $this->title,
-            'NewWindow' => $this->newWindow]
+                'Link' => $this->getLink($gridField, $record, $columnName),
+                'ExtraClass' => $this->getExtraClass(),
+                'Title' => $this->title,
+                'NewWindow' => $this->newWindow
+            ]
         );
 
         $template = SSViewer::get_templates_by_class($this, '', __CLASS__);
@@ -229,6 +231,7 @@ public function setTitle(string $title)
 
     /**
      * Get the value of newWindow
+     * @return bool
      */
     public function getNewWindow()
     {
@@ -238,12 +241,12 @@ public function getNewWindow()
     /**
      * Set the value of newWindow
      *
+     * @param bool $newWindow
      * @return $this
      */
     public function setNewWindow($newWindow)
     {
         $this->newWindow = $newWindow;
-
         return $this;
     }
 }
diff --git a/src/GridFieldTableButton.php b/src/GridFieldTableButton.php
index 43486e6..9884095 100644
--- a/src/GridFieldTableButton.php
+++ b/src/GridFieldTableButton.php
@@ -46,7 +46,7 @@ abstract class GridFieldTableButton implements GridField_HTMLProvider, GridField
     protected $fontIcon;
 
     /**
-     * @var string
+     * @var int
      */
     protected $parentID;
 
@@ -66,7 +66,7 @@ abstract class GridFieldTableButton implements GridField_HTMLProvider, GridField
     protected $promptDefault;
 
     /**
-     * @var array
+     * @var array<string,mixed>
      */
     protected $attributes = [];
 
@@ -82,6 +82,9 @@ public function __construct($targetFragment = "buttons-before-right", $buttonLab
         }
     }
 
+    /**
+     * @return string
+     */
     public function getActionName()
     {
         $class = (new ReflectionClass(get_called_class()))->getShortName();
@@ -90,6 +93,9 @@ public function getActionName()
         return strtolower(str_replace('Button', '', $class));
     }
 
+    /**
+     * @return string
+     */
     public function getButtonLabel()
     {
         return $this->buttonLabel;
@@ -97,6 +103,7 @@ public function getButtonLabel()
 
     /**
      * Place the export button in a <p> tag below the field
+     * @return array<string,mixed>
      */
     public function getHTMLFragments($gridField)
     {
@@ -107,7 +114,7 @@ public function getHTMLFragments($gridField)
             $action,
             $this->getButtonLabel(),
             $action,
-            null
+            []
         );
         $button->addExtraClass('btn btn-secondary action_' . $action);
         if ($this->noAjax) {
@@ -161,7 +168,7 @@ public function getAttribute($name)
 
     /**
      * @param $gridField
-     * @return array
+     * @return array<string>
      */
     public function getActions($gridField)
     {
@@ -170,10 +177,10 @@ public function getActions($gridField)
 
     /**
      * @param GridField $gridField
-     * @param $actionName
-     * @param $arguments
-     * @param $data
-     * @return array|\SilverStripe\Control\HTTPResponse|void
+     * @param string $actionName
+     * @param array<mixed> $arguments
+     * @param array<mixed> $data
+     * @return array<mixed>|\SilverStripe\Control\HTTPResponse|void
      */
     public function handleAction(GridField $gridField, $actionName, $arguments, $data)
     {
@@ -203,7 +210,11 @@ public function handleAction(GridField $gridField, $actionName, $arguments, $dat
                 if ($this->progressive) {
                     $response = $controller->getResponse();
                     $response->addHeader('Content-Type', 'application/json');
-                    $response->setBody(json_encode($result));
+                    $encodedResult = json_encode($result);
+                    if ($encodedResult === false) {
+                        $encodedResult = json_last_error_msg();
+                    }
+                    $response->setBody($encodedResult);
 
                     return $response;
                 }
@@ -231,6 +242,7 @@ public function handleAction(GridField $gridField, $actionName, $arguments, $dat
 
     /**
      * it is also a URL
+     * @return array<string,string>
      */
     public function getURLHandlers($gridField)
     {
diff --git a/src/GridFieldTableLink.php b/src/GridFieldTableLink.php
index 4e613e8..0735581 100644
--- a/src/GridFieldTableLink.php
+++ b/src/GridFieldTableLink.php
@@ -3,6 +3,7 @@
 namespace LeKoala\CmsActions;
 
 use ReflectionClass;
+use SilverStripe\Forms\GridField\GridField;
 use SilverStripe\Forms\GridField\GridField_HTMLProvider;
 
 /**
@@ -34,7 +35,7 @@ class GridFieldTableLink implements GridField_HTMLProvider
     protected $fontIcon;
 
     /**
-     * @var string
+     * @var int
      */
     protected $parentID;
 
@@ -54,7 +55,7 @@ class GridFieldTableLink implements GridField_HTMLProvider
     protected $promptDefault;
 
     /**
-     * @var array
+     * @var array<string,mixed>
      */
     protected $attributes = [];
 
@@ -66,6 +67,7 @@ class GridFieldTableLink implements GridField_HTMLProvider
     /**
      * @param string $targetFragment The HTML fragment to write the button into
      * @param string $buttonLabel
+     * @param string $actionName
      */
     public function __construct($targetFragment = "buttons-before-right", $buttonLabel = null, $actionName = null)
     {
@@ -102,6 +104,8 @@ public function getButtonLabel()
 
     /**
      * Place the export button in a <p> tag below the field
+     * @param GridField $gridField
+     * @return array<string,mixed>
      */
     public function getHTMLFragments($gridField)
     {
@@ -157,7 +161,7 @@ public function setAttribute($name, $value)
 
     /**
      * @param string $name
-     * @return string
+     * @return string|null
      */
     public function getAttribute($name)
     {
@@ -168,6 +172,10 @@ public function getAttribute($name)
         return null;
     }
 
+    /**
+     * @param GridField $gridField
+     * @return array<string>
+     */
     public function getActions($gridField)
     {
         return [$this->getActionName()];