One idea: open your <mission>.map file in a text editor (e.g., notepad). Search for "atdm:map_of" and see if there is more than one entity of that type. That will at least confirm that there is only one map_of entity.
I remember having to make my lute player stone deaf and blind as a bat in my first mission to pull it off haha.
I'm now beta testing my newest mission, and we've run into a bug where the player spawns with two area maps. One called "map" and the one that I have defined in the game with an "atdm:map_of" entity. Does anybody know what the issue could be? I've looked through my entity list and it doesn't appear that I have two map_of entities in the editor. It's also not an item that can be bought in the store. I'm completely stumped on this one, even though it does sound kind of familiar like I had the same or similar problem with my first map.