Created attachment 146586 [details]
An Example how Libreoffice looks after plugging out the second monitor.

SUMMARY
***
NOTE: If you are reporting a crash, please try to attach a backtrace with debug symbols.
See https://community.kde.org/Guidelines_and_HOWTOs/Debugging/How_to_create_useful_crash_reports
***


STEPS TO REPRODUCE
1. Setup a second monitor with highest border higher than the border of another monito
2. Drag a window from the higher screen horizontally to the other screen
3. Remove the second monitor
(this is only an example, it happens randomly and without doing that)

OBSERVED RESULT
The Window of a program (not fullscreen mode) exceeds the top border of the screen, so that parts are missing.
This happens randomly when opening programs, probably because of the second monitor but maybe not.
There is no hard border for windows on the top of the screen, like there is none on the bottom, but the control buttons are on the top.

Maximizing the window solves this always, going into Fullscreen mode doesnt.

EXPECTED RESULT
There should be a hard border for windows at the top edge of the screen? So that they just cant exceed it. 
When using a second monitor with hight higher than the other, you have a border there, so that you can only drag the window to the other one, when it doesnt go beyond the top rim of the screen.

SOFTWARE/OS VERSIONS
Operating System: Kubuntu 21.10
KDE Plasma Version: 5.24.0
KDE Frameworks Version: 5.90.0
Qt Version: 5.15.2
Kernel Version: 5.13.0-28-generic (64-bit)
Graphics Platform: X11
No NVIDIA Graphics