Sometimes, when a named map is placed in a chest, returning to the chest later shows the map name as "Unknown Map".

I am yet unable to determine the steps to reproduce this consistently, however here is what I know (or think I know):

• The name is not permanently changed; it returns to its correct name when the map is moved into inventory. Also, the map contents are not lost, no issue there.
• The name is always displayed correctly when initially dropped into the chest. It is only when returning to the chest later that it changes to "Unknown Map".
• It doesn't happen to every map, sometimes it only happens to a few maps in a chest. It seems related to whether the map is in use or not. In particular, I've seen the following so far:
  • I've never seen it happen to a map with a clone in my inventory.
  • I've never seen it happen to a map with a clone in an item frame near the chest.  
  • I've seen it happen to a map with no clones outside the chest.
  • I've seen it happen to a map with a clone in an item frame that was in a far away chunk from the chest.
• It doesn't happen immediately. Sometimes returning to the chest shows the correct name, then later it changes to "Unknown Map". So it might be related to distance walked from the chest - I tend to notice it after returning from a long journey. Otoh it could be related to quitting the game and returning. Unable to determine yet.
• I've never seen it correct itself on its own, it always requires moving the map back into inventory.

The consequence is it is very difficult to determine which map you are removing from a chest. In cases where multiple maps are affected, including the one you are looking for, you must move each map to your inventory in turn to see its name in order to find the one you want. It is not a major consequence, but it is inconvenient.

I will post here if I notice anything else.