When you make a map, the map is given an #id number, locked or not state, scale, level. If you put that map in a container leave the game and join again, the map is shown as “unknown map”.
STEP TO REPRODUCE :
Open a 1.21.11 world
Open a map
Should be as image 1
Put it in a container
Leave the game
Rejoin
”unknown map”
Also MC-301913 makes map loose their ID when renamed
Environment
1.21.11 no mods
Verified in 1.21.10 too with mods
Linked issues
Attachments
Comments 2
Thank you for your report!
We're tracking this issue in MC-157590, so this ticket is being resolved and linked as a duplicate.
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this is entirely intended behaviour