The bug
After taking a treasure or explorer map in your inventory the hover text of the item should show information about it (might not be the case in the trading GUI: MC-118141).
However, if you place them in a container block (e.g. chest), then reopen the world and open the container the maps show again only "Unknown Map".
How to reproduce
Obtain a treasure or explorer map (e.g. by trading) and place it in your inventory
✔ The item tooltip should now display information about itPlace the map in a chest
Close and reopen the world
Open the chest and hover over the map
❌ It shows "Unknown Map" again
Linked issues
Attachments
Comments
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Done, thanks

I can confirm this bug.
The information for Treasure maps does not show up when the map is in a chest. To get the information, the map must be transferred to a player's inventory and then it shows up for the map in the chest as well.
1. Have a Treasure map in a chest, after saving and exiting the game.
2. Place mouse pointer over map -> information does not show up
3. Transfer the map to the player's inventory -> information will show up as soon as the map is dropped into the inventory
4. Place the map back in the chest -> information shows up
Forward-resolved towards MC-157590
Done, i hope the screenshots will enought