This could be related to OpenGL texture sizes or something similar. Unity7 (Compiz) has workarounds to avoid that limitation. And Xfce avoids it by not using hardware accelerated compositing at all (last I checked). It's not surprising if only Gnome Shell hits a problem like this...
Do you get the same bug logging in to "Ubuntu" vs "Ubuntu on Xorg"? -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1725836 Title: No more than 2 displays work simultaneously To manage notifications about this bug go to: https://bugs.launchpad.net/mutter/+bug/1725836/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs