Forge version: Dont think that counts for the bug
Twilight Forest version: Could be any EDIT: 2.4.0.111 (2.3.8dev)
Link to crash log: None

This was originally said on the Twi. Forest Discord Server!

VERY troublesome bug with Magic Map: If you relog and it's in a chest, it says "Unknown map" instead of the scaling information, and when you put it into your inventory, it says the scaling information BUT all of the structure icons are gone!! EDIT 2: the map still works, you just have to remap the structures and you can still see everything previously mapped only the structures disappeared

-ZombieEnderman5 (A user on the twi forest discord server)

Might be a vanilla bug, seems to happen to the vanilla maps as well.

Can confirm this issue is a bug in vanilla Minecraft. https://bugs.mojang.com/browse/MC-118138

Duplicate of #29