Ok, it does not seem to be a VEP-problem.
I just bounced down every track to audio-files for a clean new stem-project just for mixdown.
And
AGAIN I got a BUS that is not handling automation as usual. Then I fiddle around quite a lot, and suddenly it works.
Try out another Bus - boom, same odd behavior again. No trying to fiddle again. But it's not easy to reproduce.
Must have to do something with the order in which certain buttons are pressed.
OK, it seems, I found it:
You may not automate EQ-button-on and then tweak the curves.
You may not automate EQ-button-on and start the next automation recording BEFORE the EQ-button is set to on.
=> You must automate the EQ-button-on first, and then, in another go, starting when the EQ-button is
already on (this is the important part), then automating the buttons works correctly and the curves are moving accordingly.
This is X1 only, in X2 they said they overhauled automation big time. So I guess, this problem is gone in X2.