So i tried a new clean install with 15.10 and now it works very nicely! I'm suspecting the upgrades from 14.10/15.04 or the troubleshooting steps have broken something.
I also got a reason why the 2x4k and 1x2k resolution does not work; "exceeds 3D hardware limit (8191, 8192)" I made a screenshot of the full error. I'm still curious if this could be fixed in Ubuntu as it does seem to work in Windows. It might not be a serious issue and not at all required for me, but if this proves to be an underlying issue in Ubuntu with higher resolutions this might be a problem in the future with all the high-res screens that are coming. ** Attachment added: "exceeds 3D hardware limit.png" https://bugs.launchpad.net/ubuntu/+source/compiz/+bug/1459613/+attachment/4531044/+files/exceeds%203D%20hardware%20limit.png -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1459613 Title: connecting 2x 4k screens on a Dell XPS12 (9Q33): compiz crashed with SIGSEGV in GLTexture::matrix() from GLScreen::glPaintCompositedOutput To manage notifications about this bug go to: https://bugs.launchpad.net/compiz/+bug/1459613/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs