SUMMARY

Kwin crashes often when triggering the hot-corner (present all windows) and then leaving it again (no action). This might be related to an asymmetric dual-monitor setup (4k + FHD).

STEPS TO REPRODUCE
1. Go to hot-corner
2. Leave hot corner (all windows presented)
3. Go to hot-corner again (to cancel)

OBSERVED RESULT

Kwin crashes but recovers instantly. KDE crash handler is started. Some windows are left shifted upwards (by the size of the top window decoration which disappeared briefly).

EXPECTED RESULT

Kwin should not crash and all windows should be arranged again like before step 1.

SOFTWARE/OS VERSIONS
Operating System: Linux 5.8.0-29-generic x86_64
Distribution: Ubuntu 20.10
Linux/KDE Plasma: 5.19.5
(available in About System)
KDE Plasma Version: 5.19.5
KDE Frameworks Version: 5.74.0
Qt Version: 5.14.2

ADDITIONAL INFORMATION

Configured 6 virtual desktops, total of 26 windows spread across desktops. Left monitor resolution is 4K, right monitor Full-HD.
Generated backtrace didn't look helpful, but here it is anyway:

Application: KWin (kwin_x11), signal: Segmentation fault

[KCrash Handler]
#4  0x00007f52318454ee in KWin::Workspace::workspaceEvent(xcb_generic_event_t*) () from /lib/x86_64-linux-gnu/libkwin.so.5
#5  0x00007f52304bd4ef in QAbstractEventDispatcher::filterNativeEvent(QByteArray const&, void*, long*) () from /lib/x86_64-linux-gnu/libQt5Core.so.5
#6  0x00007f522a20f505 in QXcbConnection::handleXcbEvent(xcb_generic_event_t*) () from /lib/x86_64-linux-gnu/libQt5XcbQpa.so.5
#7  0x00007f522a210a46 in QXcbConnection::processXcbEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /lib/x86_64-linux-gnu/libQt5XcbQpa.so.5
#8  0x00007f522a233740 in ?? () from /lib/x86_64-linux-gnu/libQt5XcbQpa.so.5
#9  0x00007f52304bea4b in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /lib/x86_64-linux-gnu/libQt5Core.so.5
#10 0x00007f52304c6fc6 in QCoreApplication::exec() () from /lib/x86_64-linux-gnu/libQt5Core.so.5
#11 0x000055f0a8042a6d in ?? ()
#12 0x00007f522fe46cb2 in __libc_start_main (main=0x55f0a80426a0, argc=3, argv=0x7fff6de06788, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fff6de06778) at ../csu/libc-start.c:314
#13 0x000055f0a8042f8e in _start ()
[Inferior 1 (process 1651208) detached]