I have just reinstalled my Leap 42.1 system on which I didn’t have this problem but strangely now I do have it.
I go to Configure Desktop (systemsettings5) and in Display Configuration I set my second monitor to be rotated 90deg clockwise. Everything works fine until I logout - then I have to do it again and again after each logout/reboot.
The only difference between my current installation and the previous one is that the previous one was upgraded from 13.2 x64. However I did not format the home partition and nothing should be changed in there.
What is the reason for that and how can I fix it?