They co-operated wit the factory and didn't find the true reason. There is a voltage breakdown to 11.5 Volts during the engine start and they do not know why. Most of the S diesels don't have this problem, but two more at my Porsche Centre do.
Porsche Stuttgart says, they have no solution this time. So I have to live with that or give back the car.
They handed over a document to me that says, the issue will get solved with no costs, as far as Porsche knows, how. Maybe never...