All right, back from the range, was able to zero it.
What I realized, the illumination zero is a bit squishy.
You have to concentrate to not miss it, and if you don´t it is also easy to "overtravel" it.
Then something a bit odd happened.
After boresighting and making the first two shots, I corrected elevation and windage, as usual.
But the following shot was off, not where it should be after the correction.
I was wondering where that came from.
So I´ve made another shot, and the hit was where it was supposed to be, same thing with the 3rd one.
Wth?
To test it, I turned 10 clicks up und ten clicks left, the first shot was off, the 2nd and 3rd were where they should be.
Going back to zero it happened again, all in all I could repeat it four times, before I ran out of ammo (had only 20 rounds with me to make a fast zero).
I have no explanation at this point.
If it would be the mount, it would happen after shooting, but not after turning the knobs.
Any explanation?