Hello,

Sometimes I'm experiencing a strange bug on my system where the major part of the UI becomes completely unresponsive to mouse events. I have no idea which component of KDE (or maybe even anything else) could cause this, that's why I'm filling the report against the 'general' component.

SYMPTOMS
- During normal work suddenly only one window reacts to mouse events (clicks, hovering), everything else completely doesn't (including Plasma panels, window decorations etc.).
- All windows still receive keyboard events as usual when in focus, and thus can be controlled by keyboard
- Switching windows via Alt-Tab doesn't help in regard of the unresponsivness to mouse events.
- Sometimes (not always!) windows that didn't have focus when the bug occurs react "partly" to mouse events: They seem to register clicks but the actions triggered by the clicks seem to hint that the clicks are registered on totally different places of the window compared with the actual cursor position on the screen (and thus making it rather impossible to control the application via mouse)

STEPS TO REPRODUCE
Found no way how to trigger this by any specific action. It happens randomly during normal work without being able to recognize a specific pattern.

ADDITIONAL INFORMATION
- Sometimes possible to recover to normal behaviour by window switching/random user interactions (mouse, keyboard), but most of the time only logging out out the session helps (restarting kwin or plasmashell does _not_ help)
- Seems the pointer is grabbed by something: If I try to run xprop it imediately exits with an error message ("xprop: error: Can't grab the mouse.")
- Frequency of occurence varies, from happening two times a day to one occurence in 1-2 weeks
- Has happened for at least 1½-2 years (as long as I'm using KDE), so not a recent regression
- I think I MIGHT have seen this outside of my main installation (the problem with a separate installation for testing purpose is that I need to use it for a sufficent long time to give the bug a chance to appear)

If there is any way how I can help further debugging this, I'll try my best.

Kind regards,
Jan

SOFTWARE/OS VERSIONS

Distro: Kubuntu 20.10
Qt version: Qt 5.14.2
KDE Plasma version: 5.19.5
KDE Frameworks version: 5.74.0

Output of 'lshw -class display':
(just in case this is related to my graphics)
  *-display                 
       description: VGA compatible controller
       product: Oland PRO [Radeon R7 240/340]
       vendor: Advanced Micro Devices, Inc. [AMD/ATI]
       physical id: 0
       bus info: pci@0000:01:00.0
       version: 00
       width: 64 bits
       clock: 33MHz
       capabilities: pm pciexpress msi vga_controller bus_master cap_list rom
       configuration: driver=amdgpu latency=0
       resources: irq:29 memory:e0000000-efffffff memory:f5000000-f503ffff ioport:b000(size=256) memory:c0000-dffff