Seems like we sorted it out...
It should have been a cold starter problem.
Somehow the car is on cold start even if it is hot.
Removing the connection does the trick.

Now I have to decide if it will be a switch somewhere or a root cause analysis 🤪

Thank you for your input an ideas!

1973 2CV AK400 Ralley
1985 plus 4 four seater
1992 Peraves ecomobil
bicycles (pedersen to recumbent)