recently almost all interface functions open in another window whenever slicer is in full-screen view.
I’m using 5.3 on Mac OS Venture Version 13.3.1 with Apple M2 Pro
Probably popups appear in the application’s screen.
Do you move the application to a different screen after you start it?
Does it help if you delete Slicer.ini settings file? (in the slicer.org subfolder in your user profile folder)