https://bugs.freedesktop.org/show_bug.cgi?id=73530
--- Comment #34 from Paul Menzel paulepanter@users.sourceforge.net --- 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.