Custom block menu Z-fighting

Whenever I go to edit a custom block or look at a help screen, and have a few "windows" open at the same time, sometimes they will start Z-fighting.
(Picture deliberately taken in hopes of occurrance.)
This only started happening a few days ago and it's really annoying.
Could someone look into this?
Edit: Turns out it's just my browser not having been updated, never mind

It's a bug in recent Chrome version, please update Chrome to the currrent version (v87), that'll fix it.

Ah ok