From version of 5.9.3 (5.9.2 was ok) screen configuration doesn't stay the same as was set. I have 2 user accounts and on one I have split outputs and on the other I have connected outputs. Since version 5.9.3 (current) the second account screen splits outputs by itself every time I reboot computer. I suspect that it gets configuration from my first account.
I have found solution to this problem. I had "KEkran 2" turned off in background services. Something changed after 5.9.3 KDE update that I had to turn on so it didn't split my screens. I don't have split screens configuration anywhere except my second user account so I don't understand why in version 5.9.3 it is taken from that other user account even when I don't have screen services turned on.
Thanks for the note!