Comment # 1 on bug 1173727 from Fabian Vogt

(In reply to Simon Vogl from comment #0) 
> Recently I noticed that plasmashell reports a crash in system tray after
> logging out and back in again a few times. At first plasma still seems to be
> working, but what's noticable is that all applications tend to start up A
> LOT slower.
> It never happens on first login, but after a few logins its easily
> reproductible even in a VirtualBox VM.

I can't reproduce the issue here at all, it might be related to the
configuration, e.g. plasmoids or other settings. Can you try with a clean user
account?

> ...

> I've attatched a full stack trace with all debugsymbols installed, maybe
> that helps.

If I'm not mistaken, it shows that it tries to unload
/usr/lib64/qt5/qml/QtQuick/Controls/libqtquickcontrolsplugin.so while
plasmashell is still running in a separate thread - that looks very weird.
Can you attach with gdb and try to get a deeper backtrace of all threads?

> Thanks for your efforts,
> DarkWav