Sometimes, when I enter full screen mode with an app, the notch bar is moved to the bottom part of the screen as showed in the screenshot. It stays like that until I restart BTT or toggle the notch bar visible/hidden.
I often use an iPad as a 2nd screen with Sidecar, but this happens quite often also while my iPad is off. It's probably unrelated, but while I'm using the iPad, the mini menubar is not displayed.
In my experience, this seems to be triggered by full screen mode. Not all apps do this. For example, it never happened with Finder so far, but BTT seems to trigger the issue every single time I enter full screen mode. Occasionally, navigating spaces triggers the issue as well or makes the notch bar disappear, but this seems to happen less consistently. I'll record the screen and send you an email later on so you can see it yourself.
Let me know if I can do/check something to help you figure it out.