For a comprehensive list of other examples of issues with 2D planes in models not being mirrored as expected, click here.
The bug
The planes composing the chain on lanterns do not mirror on the back as one would expect, resulting in physical/illogical weirdness.
Fixed models (Mojang has full permission to use this fix):
[media][media]
May be intended for floor lanterns, however should be valid for hanging lanterns.
How to reproduce
Place a hanging lanterns
View a specific section of the chain
View the exact same section of the chain on the direct opposite side
Note that the exact texture pattern at that position is different, even though it should be the same
Hi, I can confirm for 1.16.4 prerelease 2.