"Empty Map" turned into "Buried Treasure Map" which can still be used as normal empty map.The situation didn't change even after i changed the language.
When i was aware of this bug i've already returned to my house and failed to reproduce it. Before that, i was rowing my boat searching for treasure maps. I had four same treasure maps and two empty maps in hand, which were found in different chests. I left three treasure maps in a chest when my backpack was full. I left the last treasure map in the treasure chest. When i was back home, the two empty maps turned into "Buried Treasure Map", and to test whether they can still be used as normal empty map, i used one of them. Over