XnView Software

No, it seems to work just fine when I go from browser directly to full screen.

Could there be some incompatibility with High Sierra and the newer Qt versions?

Fresh install, open XnViewMP, then photos folder, single view, and then fullscreen mode.
The first image is displayed correctly, but the next ones don't. The only thing I see is a bar with a portion of the next photo on the top of the screen, and also under the on screen playback controls.
This ...

This bug here https://www.xnview.com/mantisbt/view.php?id=1784 is still present on my configuration: macOS High Sierra 10.13.6 on a late 2011 Macbook Pro.
I am still stuck on version 0.94.3, the last one with working fullscreen mode. I tried every update since that and none works.