Gnome 3.36 flickering framebuffer line above status bar

[meist3r]

I'm encountering this problem in both Ubuntu 20.04 and Pop OS 20.04.
When I boot the default X11 session on my AMD graphics card

01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Oland PRO [Radeon R7 240/340]

I get a 1 pixel line above the Gnome status bar that flickers seemingly with screen refreshes and shows parts of the current frame buffer. You can sometimes tell that parts of my open browser window (bookmarks bar) are being displayed there. If the screen and applications on display are very quiet there isn't much movement but when I move the mouse or hover over (browser) elements that are seemingly refreshed periodically the line flashes and redraws with content from the screen.

When I don't move the mouse or do much at all the flickering dies down after a while because there is not much refresh going on. During regular use though, the whole thing is super annoying.

This is showing the behavior, this site open in Firefox, typing the words.
"this is me typing this comment right now."

https://youtu.be/j1JI5ST0ZkM

This exact problem occured to me on a fresh install of Ubuntu 20.04 via USB media. For a bit it's fine and then this corruption happens. The video is taken from a POP_OS 20.04 installation on the same machine that shows the exact same behavior for the AMD GPU after a fresh install.

If I switch to Wayland this never happens.

[meist3r (meist3r)]

I can suppress the behavior temporarily by switching the resolution of making any changes to the Display settings that cause a refresh (e.g. change to a lower resolution). Simply discarding the changes will give a working session. Reloading the GNOME session will only very briefly affect the phenomenon.

[Ricardo Garicano Arenas (rgaricano)]

 also have a similar problem with xubuntu & ubuntu studio (with updated &/or fresh install, but not with test version), the screen is "broke" in different displaced strips.
I fixed it (temporarily) increasing the framebuffer in 1 pixel
eg: xrandr --fb 1441x900 --output DisplayPort-0 --mode 1440x900 --panning 1440x0