Package: plasma-workspace
Version: 4:5.8.4-1
Bug: #846389
Today was released xserver 1.19.1.
So I have reinstalled xserver-xorg-core 2:1.19.0-3 and verified the return of the problem.
Subsequently I have compiled new source and reinstalled it on existing packages.
After logout and relogin I have tested my system and... no problem!
Then I Restored previous version 2:1.18.4-2, I will wait new version provided by the distro.
Thanks