Weird graphics glitches in Messages.app on macOS Big Sur

I’ve been experiencing this bug since the Messages.app rewrite in Big Sur. I have so far not been able to find out what exactly causes it: Often, but not always when I want to respond to a thread, the colors of the interface will freak out when it brings the thread to the forefront. The colors are always different, see also this video:

Only after it happened the tenth time did it occur to me to check if causing a “redraw” by dragging another window over it might fix the rendering. As you can see above, it certainly does… something.¹

Why am I filming and photographing my screen? Well as it turns out, this does not show up in screenshots or screen recordings at all. They look perfectly fine, so it must be a bug fairly “late” in the graphics pipeline, I suppose? Pinky promise, video and photo have not been modified in any way except for the blurring of personal details.

Leaving threaded mode or closing the app fixes it, also there is no high CPU load or anything like that when it’s happening, and the app is still perfectly usable (well, as usable as it is without weird graphics glitches).