Map crashes game when picked up if it has signs in the area

Me and my friend went to pick up and update the maps that where in a 3x3 block high formation. Once he took out the middle map, it crashed his game and didn't allow him in the server, the error was internal exception, he then managed to throw it out of his inventory and it stopped crashing. I then picked it up and started getting the same error and the same things happened until I managed to drop it.