The second player on a Hosted World cannot save the Updates to their Map. They are always reset when then player disconnects. The Host of the world's map always saves. I'm always the second player and it's annoying having to remember which islands are N, NNE, NE, NEE, E, SEE, SE, SSE S, SSW, SW, SWW W, NWW, NW, NNW and back to N. Makes navigating very rough and a bit annoying.