Bug 416671

SUMMARY
Sorry I couldn't word the title better, but basically here's the display setup I currently have:

1x Monitor @ 1920x1080 (left side)
1x TV @ 1360x768 (right side)

So to reproduce this, I'm afraid having a secondary monitor is necessary.


STEPS TO REPRODUCE
1. Open Plasma's Display Configuration tool: kcmshell5 kcm_kscreen
2. Enable your secondary screen, side-by-side in my case. Leave the tool open for now
3. Open a new Konsole window (Ctrl+Alt+T), drag it onto your secondary screen
4. Hit F11 to enter full screen mode in Konsole
5. Go back to the Display Configuration tool, disable your secondary screen now
6. The Konsole window, which was in full screen mode on your secondary screen, is now moved to your primary (and only) screen, so far so good
7. Now, hit F11 to leave full screen mode on Konsole


OBSERVED RESULT
Once you do that last step, the Konsole window will actually disappear and move back to your secondary screen. And even though this Konsole window still shows up in the Task Manager widget, once you try to activate the window, KWin will raise it on your disabled secondary screen again. So, since the window is now out of bonds, you can't use your mouse to drag it back onto your primary screen.


EXPECTED RESULT
Once you leave full screen mode, the window should stay in the first screen, instead of moving back to the disabled secondary screen.


SOFTWARE/OS VERSIONS
Linux: Arch Linux, kernel 5.4.13
KDE Plasma Version: 5.17.5
KDE Frameworks Version: 5.66.0
Qt Version: 5.14.0


ADDITIONAL INFORMATION
I was also able to reproduce this with a Chromium tab in full screen mode.