This bug occurs mainly when there is an external building imported from a third party software into a Single Player map. When playing that map, I approach to the imported building and a list of "Unable to locate sign" commands appear in chat. When I search for those signs, their text disappeared. My toughts on this are that since the imported schematic was not built in the world I am playing,then the game read it as if it's part of another "world", so whenever I go into that zone the signs get affected by that bug (or at least that's what I think). I hope this is enough information to resolve it. Thanks in advance.