Thanks for your reply Phlim. If you mean that the backported version was intended to fix the issue, it didn’t, at least not in my case cause I’m still having that issue even with 6.5.4-3 
I never had the problems on 6.5.3, with 12-08 update. Even on KDE’s bugtracker, the first version reported in was 6.5.4. There, the KDE Devs said that the fix will arrive in version 6.5.5 (but they asked distro maintainers to backport it, yes I know).