Error in my Stop Transaction implementation for OCPP 1.6

[J0ergL]

Dear community,

my implementation for Stop Transaction from a charge point views is not working.

     async def stop_transaction(self, transaction_id, connector_id, reason):
        ticks = 250
        request = call.StopTransactionPayload(
            meter_stop=ticks,
            timestamp=datetime.utcnow().strftime('%Y-%m-%dT%H:%M:%S') + 'Z',
            transaction_id=transaction_id,
            reason=reason,
        )
        response = await self.call(request)

the last code line is executed and the routine drops out.
Is the format of the payload incorrect?

I'll gladly supply more information on request.
Thank you

[J0ergL]

Anyone?

[J0ergL]

It seems it is related to the used CS, it works with a local CS (SteVe) but not with the used CS.