Twice in the last two days the system has completely frozen while I was resizing a window. The first time I was resizing a Konsole window. The second time I was resizing a Firefox window. Both times the system was completely frozen and to recover I had to reset by holding the power button for 5 seconds.
This is on X11 or Wayland?
This is on X11.
Is the mouse cursor still moving when the system is frozen.
No, the mouse cursor is frozen too.
In that case: it's not KWin. The mouse cursor is provided by X and this means that X is frozen. You need to report to X developers. Btw. it's quite likely that X is also a victim. As you mention Konsole it is possible that this is a graphics driver issue.
Okay, thanks Martin.