Hi, took me some time, but I finally uninstalled pinballx and reinstalled 32bit version. Now all is great and i am generating the video’s out of pinballx. Really super! I also managed to set the backglass correctly of the Avengers. I played a little with the settings, but unfortunately cannot reproduce the issue anymore to tell you which setting did the trick.
So thank you all for you hints and tips here. It certainly helped me!