I updated TheSkyX to the latest build and @Focus2 started working again!
So, I tried to set it up. I calculated a range of 452 steps for @Focus2. But when I ran it for the first time, the difference apparently wasn't big enough. So, I extended it to 800 steps, but I also increased the sample number from 10 to 20 to make sure that I get enough samples - especially within the V.
And - voila! Worked at first try. Of course it took some time (20 samples averaged over 5 images!) But focus was great. Tomorrow night, I will play with it more and try to improve these parameters to make it faster.
To my surprise, @Focus2 never asked me for covering the scope because it wants to take darks. I noticed that I had 'None' in the Reduction drop-down selected. I didn't realize that this feld is used for the @Focus2 routine ...
After that I tried autoguiding. It also worked again. I could get it calibrated and working in PHD really fast. But in TheSkyX I couldn't get it to work. But I didn't even try to improve my polar alignment - that could explain it. Will try later again.