SUMMARY
***
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***


STEPS TO REPRODUCE

I have no idea

OBSERVED RESULT

All started when Thunderbird froze and stopped responding. I don't know whether that was what triggered the issue, or if was a consequence of it.
I then clicked on the Task Manager icon of a terminal, with the intention of using the terminal to kill Thunderbird, but then everything started going berserk. The easiest part to describe and the most noticeable thing was: All the animations of windows being minimized and restored, would leave "trails" - see the screenshot. Every once in a while it looked like everything went back to normal, but then it would start again. This went on even after successfully killing Thunderbird. In the end I had to reboot.

Look at the attached screenshot: you just need to know that I did NOT have many terminal windows open, just one. 
The red rectangles are not part of the issue: I needed to hide potentially sensitive information.

When trying to reboot, the shutdown got stuck at a black screen with a bunch of errors or messages. I attach a picture I took. I had to use REISUB to complete the boot.

EXPECTED RESULT

None of this crap should happen

Operating System: Manjaro Linux 
KDE Plasma Version: 5.27.10
KDE Frameworks Version: 5.112.0
Qt Version: 5.15.11
Kernel Version: 6.1.68-1-MANJARO (64-bit)
Graphics Platform: X11
Processors: 8 × Intel® Core™ i7-1065G7 CPU @ 1.30GHz
Memory: 7.3 GiB of RAM
Graphics Processor: Mesa Intel® Iris® Plus Graphics
Manufacturer: LENOVO
Product Name: 81WE
System Version: IdeaPad 3 15IIL05