Fullscreen doesn't work

I have a problem with Vis-Players config.ini.

Windows Default Zoom in the Display Settings is at 125%.
When I launch my game with RESOLUTON=DESKTOP or AUTO,
The game is not shown in fullscreen, it is just showing about 3/4 of the screen in the upper left corner.

Only when I set my Zoom Settingsin Windows to 100% I get fullscreen.

This is quite annoying since customers are mostly at default settings.

Any Idea how to fix that? I want to get rid of an extra launcher tool to enter a fixed resolution.