It could be any number of things, but that's my best guess (unfortunately it's also a production server, so that complicates any sort of troubleshooting). Maybe it's a gpu memory leak? Anyway it only seems to affect the graphics subsystem, as everything else including ssh, apache and mysql keep on trucking.
I'd heard that the open source 'nouveau' driver could be problematic, this is the only pc with their graphics I use, all the others are either AMD or Intel, with no similar issues (or any, really) -- I always install the headless netinstall server edition, add xfce, and build up from there as needed (my home pc runs Fedora).
Totally not a fan of Gnome or KDE. Tried cinnamon, found it buggy and lacking polish but this was a few years ago.
I usually try to id all running GUI processes in top (typically firefox and thunar), and kill them before xserver and reboot.
EDITED: 23 Mar 2022 15:48 by DSMITHHFX