Hello Joachim,
yes, everything is the same, on my development machine. The error shows up on every page creation.
But OK, the error seems to be so unprobably, that I dare going online these days and give the control to my customer.
I tried strange things in the development process. Nested conditional conclusions all over. Maybe the error has established while doing these strange things. Now my code has become pretty normal. New projects with the same code run without trouble. So I can live with some mystery left.
If I get a similar error again, I will inform you. And I store the erroneous project for further investigations, if new questions come up.