I had a librarian villager that traded Fortune III and a few minutes later it just traded papers and bookshelves. I didn't destroy its workstation, just placing down more for other villagers. I tested it on an other map and it looked like they change trades when they restock. It only happens if the player hasn't traded with them yet.
Linked issues
Comments 3
Duplicate of MC-156615.
Are you sure that you checked the correct villager? Also, were your villagers free-roaming or did you have them in cells?