(In reply to Johannes Hirte from comment #28)
> From the reports, it seems to be compositor related. For me, kwin with
> OpenGL 3.1 backend works fine. xfwm4 seems to trigger the bug, maybe other
> compositors too.

Confirmed that the workaround of switching to the kwin OpenGL 3.1 compositor
works for me.

kernel: 5.3.0-19-generic (Ubuntu 19.10)
window manager: kwin-x11 4:5.16.5-0ubuntu1
CPU: Ryzen Pro 2500U
machine: Lenovo Thinkpad A485
X server: xserver-xorg 1:7.7+19ubuntu12
userspace driver: xserver-xorg-video-amdgpu 19.0.1-1ubuntu1

I'm happy to test patches or reproduce.