This seems to me more like an issue with the Boox fullscreen mode with their latest firmware. Once I start transferring the annotation changes to the e-ink version (which should happen sometime this week), I'll see if the same issue occurs on the Boox Max 2 Pro. If it does not, then I'm going to need to get Onyx to work with me, which may take quite awhile. The Boox tablets don't behave like normal Android devices when it comes to the fullscreen mode. Onyx requires that in addition to telling the OS that I want the application to be fullscreen, I have to send out a special request (called an Intent) to show or hide the status bar. So based on what you are describing, their software is doing something bizarre when I tell it to hide the status bar.
Mike
Mike