I suggest that you download the Xubuntu 18.10 daily ISO, then boot into live mode and check if the issue with the open source driver is present too.
Another thing to test is to see if disabling the builtin compositor (Settings > Windows Manager Tweaks > Compositor) eliminates the glitch. -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xserver-xorg-video-nouveau in Ubuntu. https://bugs.launchpad.net/bugs/1775212 Title: Windows not painted completely since 18.04 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xfwm4/+bug/1775212/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : ubuntu-x-swat@lists.launchpad.net Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp