I don't have a good recipe for this. It has been happening occasionally
for quite some time (the attached screenshots are from 2021, but the
same thing is still occurring). Every once in a while, a part of the
Emacs frame gets into a state where glyphs from nearby lines can be
painted after the tail end of other lines. This seems to be related to
scrolling (that is, while scrolling, the glyphs replicate onto nearby
lines, but when scrolling back they stay. I usually have to force a full
repaint to get the glyphs to disappear.