i915 0000:00:02.0: [drm] GPU HANG: ecode 7:1:85dffffc, in Renderer 
i7-4790k, kernel 5.11.1-arch1-1
Issue has been present since sometime in the 5.10-series of kernels.
Windows, usually starting with Firefox, but sometimes starting with corectrl or gnome-terminal or the top bar thing in Gnome 3, will begin becoming corrupted in weird ways. This happens in X, I have yet to try it in Wayland. This corruption will accelerate and worsen until eventually a GPU hang occurs. Sometimes the system doesn't recover nicely from this GPU hang and I'll have to switch to a console with ctrl+alt+f[3-6] to kill processes to recover the system.
uname -m: x86_64
uname -r: 5.11.1-arch1-1
Linux distribution: Arch Linux
Machine or mother board model: ASUS Z97-AR, i7-4790k
Display connector: HDMI with an HDMI->DP converter on the end and DP with a DP->HDMI converter
A full dmesg with debug information and/or a GPU crash dump:
[Feb24 13:37] i915 0000:00:02.0: [drm] GPU HANG: ecode 7:1:85dffffc, in Renderer  [ +0.000008] GPU hangs can indicate a bug anywhere in the entire gfx stack, including userspace. [ +0.000002] Please file a _new_ bug report at https://gitlab.freedesktop.org/drm/intel/issues/new. [ +0.000002] Please see https://gitlab.freedesktop.org/drm/intel/-/wikis/How-to-file-i915-bugs for details. [ +0.000002] drm/i915 developers can then reassign to the right component if it's not a kernel issue. [ +0.000002] The GPU crash dump is required to analyze GPU hangs, so please always attach it. [ +0.000002] GPU crash dump saved to /sys/class/drm/card0/error [ +0.000089] i915 0000:00:02.0: [drm] Resetting chip for stopped heartbeat on rcs0 [ +0.101845] i915 0000:00:02.0: [drm] Renderer context reset due to GPU hang
I'll try to capture video if I see it happening again.