SOLVED: @Manu I did find the problem.
Somehow, and I'm not sure which process triggered this but in my /home/'your username'/.config/autostart folder there was an arandr?.desktop file. (not sure the exact filename but delete or stow away in trash anything with arandr
DELETE this file and your display preferences will work perfectly as before. Reboot or log out required before opening up display preferences again.
SOLVED: @Manu I did find the problem. /.config/ autostart folder there was an arandr?.desktop file. (not sure the exact filename but delete or stow away in trash anything with arandr
Somehow, and I'm not sure which process triggered this but in my /home/'your username'
DELETE this file and your display preferences will work perfectly as before. Reboot or log out required before opening up display preferences again.