We have come across a dupe where if a player is accessing the voidlink bag, closes the bag, and accesses their, in this case, Thaumonomicon, it removes the book and replaces it with a duplicated voidlink bag. The bag takes place of the book that was there originally. Both bags are accessible and no relogging or server restarts fixes this. I attached the ticket that was reporting this. The player notes that it is caused between the events of connection loss such as low latency spikes.