As of version 0.1.11, Picking up a filled treasure map seems to cause a packet issue which breaks a players data until the map is removed via NBTEditor, The only fix I am currently aware of is doing such with NBTEditor on their inventory. Hopefully this helps narrow down any issues.

My issue #504 is the same problem. I and none of the players that have tried logging in have any maps in their inventory. Even a brand new player gets the same error

was fixed last update thanks