Reported in CurseForge

It appears there is a Z-fighting issue with the doorknob model.
Unfortunately I can't reproduce it on my end.

Reporter claims it's fixed 🎉
Since this was apparently an issue in all versions, I fixed it everywhere.

This is definitely still happening:

(testing on 1.16 using my Nvidia card; the issue doesn't show up on my Intel card)

Turns out this was a texture rounding error, not z-fighting.