Multiple green pointers on map

When I place map into an item frame, the green pointer is displayed on the map. But when i move the map somewhere else and put it into item frame at that other place again, there are two green pointers shown on the map - new one on my map's current position, but also the first one. New green marker is added each time I move the map. I believe this is a bug as the old markers seem useless to me and because I move my maps quite offten these out-of-date markers make my maps' lucidity lower and lower through time.