If I go into the wild and activate a treasure map is there a chance it leads to previously explored locations or are they fresh every time?
I'd say there is a chance for anything. I mean the two times i activated them. Someone else was already on their way and beat me to them.
From the maps that I have used, if the mansion has been loaded into the world the maps wont lead you to them. But if you open say 5 maps at the same time, the will all lead to the same place until you find the mansion, then all new maps will lead to the next closest mansion. Also take not that you wont find any mansions <50k from spawn as they have all been found by now, so you will have to travel really far to find one.
