Comment # 17 on bug 968877 from Hardy Heroin

Actually you don't even need to reboot your system to see if you are affected.
Simply starting an application like kwrite will result in the following error
on an affected system:

kwrite: relocation error: /usr/lib64/libKF5XmlGui.so.5: symbol
_ZN15QGuiApplication35setFallbackSessionManagementEnabledEb, version Qt_5 not
defined in file libQt5Gui.so.5 with link time reference

I then made the mistake of rebooting rather than downgrading (thank goodness
for IceWM to easily recover). I can confirm the workaround in comment #12 works
(I choose to let zypper automatically downgrade whatever it suggested rather
than force it). Afterwards from the terminal I could start kwrite again without
problems.