I experienced this issue as well; while playing multiplayer via LAN (single player world opened to a friend to join) the other player created 3 map copies and placed them in item frames throughout the area covered by the map. The green arrows did not actually appear on my copy of the map until I visited the location of the item frames. Shortly after all the item frames had been "discovered" and appeared on the map the indicator arrow for the other player stopped displaying on all versions of the map (in frames and held by both of us). After meeting up with the other player we swapped maps and I temporarily dropped mine to see what effect only them holding the map had; after I picked up my copy of the map again the other player's indicator was now shown but mine was missing. The other player then dropped their copy of the map and I handed them my copy, at which point both of our indicator arrows disappeared from the map.
After deciding to do away with all the item frames to try to fix the issue we found that the map was still stuck showing only the item frames' green arrows and neither of our player indicators even though all item frames had been removed. We then placed all the map copies in a single pile inside a chest and exited the game. I later resumed the game in single player mode again and upon taking one of the maps out of the chest it quickly re-drew from blank and appeared to be functioning normally (no green indicator arrows and my white arrow correctly displayed). I have not yet tested what happens when another player gets involved again.
Edit: Bug encountered in v1.4.5 running in 64 bit java on Win7.
Further Edit: The other player says that if they weren't looking directly at the map but had it in-hand (so it as visible at an angle along the bottom of their view) they would occasionally see one of the missing player indicator arrows appear for a moment; maybe the possible z-fighting mentioned in related issues is going on between the map and the indicators?
Patrick Sullivan
I experienced this issue as well; while playing multiplayer via LAN (single player world opened to a friend to join) the other player created 3 map copies and placed them in item frames throughout the area covered by the map. The green arrows did not actually appear on my copy of the map until I visited the location of the item frames. Shortly after all the item frames had been "discovered" and appeared on the map the indicator arrow for the other player stopped displaying on all versions of the map (in frames and held by both of us). After meeting up with the other player we swapped maps and I temporarily dropped mine to see what effect only them holding the map had; after I picked up my copy of the map again the other player's indicator was now shown but mine was missing. The other player then dropped their copy of the map and I handed them my copy, at which point both of our indicator arrows disappeared from the map.
After deciding to do away with all the item frames to try to fix the issue we found that the map was still stuck showing only the item frames' green arrows and neither of our player indicators even though all item frames had been removed. We then placed all the map copies in a single pile inside a chest and exited the game. I later resumed the game in single player mode again and upon taking one of the maps out of the chest it quickly re-drew from blank and appeared to be functioning normally (no green indicator arrows and my white arrow correctly displayed). I have not yet tested what happens when another player gets involved again.
Edit: Bug encountered in v1.4.5 running in 64 bit java on Win7.
Further Edit: The other player says that if they weren't looking directly at the map but had it in-hand (so it as visible at an angle along the bottom of their view) they would occasionally see one of the missing player indicator arrows appear for a moment; maybe the possible z-fighting mentioned in related issues is going on between the map and the indicators?