Comment # 34 on bug 73530 from Paul Menzel

No idea, if it’ll give a clue, but often the display did not work even after
turning it off and on more than five times. Blindly logging out again, which
closes the X session, goes to tty1 and then back to the new X session with the
GDM login screen and logging back in, often I am able to get the display back
to work by less than four off-on xrandr cycles.