After purchasing a woodland or ocean explorer map from a villager, going into the nether or end will change the map to a blank map with a "unknown map" description. This map will stay blank until logging out of the world and logging back in again.
If a villager with an explorer map trade is taken from the overworld to the end, buying maps from him there and going through the exit portal will not turn the maps blank.
To reproduce
Buy a explorer map that has an ocean monument or woodland mansion icon on it from a cartographer
Enter the Nether
Related issues
is duplicated by
Comments
Can confirm in 21w03a.
Can confirm in 21w05a.
Can confirm. This will not fix itself upon returning into the overworld and a relog is required in order to fix this.