With plasma5 update I cannot unlock the lock screen using my password. This is
perhaps:
https://bugs.kde.org/show_bug.cgi?id=314661

If I do
# chmod 4755 /usr/lib/kde4/libexec/kcheckpass
it works again.

kdebase4-workspace.spec used to have:
%attr(-, root, shadow) %{_kde4_libexecdir}/kcheckpass

plasma5-workspace.spec has only:
%{_kf5_libdir}/libexec/kcheckpass

So running it says:
$ /usr/lib64/libexec/kcheckpass
Password: 
Information: Permissions on the password database may be too restrictive.

Hence lock screen cannot check the password.