Steps to reproduce
This issue does not appear to be a regression considering the fact that it occurs in Nightly as old as v85.0a1 and v65.0a1 or even v45.0a1.
Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:97.0) Gecko/20100101 Firefox/97.0
I can confirm this bug. The Icons are set up by multiple images with 1px height.
This bug is a duplicate of https://bugzilla.mozilla.org/show_bug.cgi?id=1164550