Comment # 20 on bug 1160995 from GCC Da DiscoveryTechnologies

The kscreenlocker-crashing-problem persist, even if all users logout. Any user
opening a session after it happened once, inherits the problem. Even if he/she
is the only one logged in, kscreenlocker crashes on every invocation.

The only remedy is to reboot the system.

Manually starting "/usr/lib64/libexec/kscreenlocker_greet --testing" with
disabled sandbox like in comment #1 works fine without coredump.

My observations with the different versions of the package seemed to be
coincidence. We now could reproduce the problem with the official package
version 5.12.9-lp151.2.4.1 , too.