I have now opened a support ticket. But as every time so far, the support is characterized by massive incompetence.
The guys have merged two tickets that have nothing to do with each other, just because I wrote an answer to both at the same time.
And then come, as always, pointless references to some support articles, which have nothing to do with the described problem.
So my experiences with the support are really worst.
But if I do get a solution, I will of course write it here.