Maps placed on walls do not update to changes made in the surrounding environment. If another player looks at a copy of the map, maps derived from that map will update on the wall (or in the frame) but not maps of the same region which were made separately. The behavior of mounted maps should be decoupled from whether or not another player has looked at the physical map.

Steps to reproduce.
1) Make a new map.
2) view it until it shows it's surroundings
3) copy the map
4) mount the original map in a item frame
5) drastically change the area the map should be displaying
6) observe no change in the map in the item frame
7) open your copy and see the difference
8) observe that the map in the item frame has now changed to show the correct information