I have been having crash issues that de spawned quite a few of my villager librarians. They have all switched beds and I was working on moving them back to their place when I broke a job block. The novice villager, with one trade completed, lost its job and trades by either resetting or changing to another job block. If I set another lecturn down, it will become a librarian again but will not keep its initial trade and reset. I break the job block and I have another empty job lying around, it will claim that block and be locked with the initial trade I completed it as a librarian and stay stuck. 

Librarian(name tagged)+(Enchanted book x cheap price)+this issue=ocd meltdown and digging holes for several hours.