Villager trades that have been locked in (traded at least once) constantly unlinked with the job block placed in front of them and linked with another identical job block. 

Example Librarian A unlinking with Lectern A placed in front of them and linking with a different Lectern, Lectern B. This causes Librarian B to unlink from Lectern B and finding another Lectern which aggravated the whole issue within a trading hall with many Librarians. 

They constantly link with job blocks away from them which they could not physically see of path find to (behind an enclose wall, buried beneath blocks, above them with no accessibility) 

As a result of the swapping of job blocks, all villagers could not restock their goods making the trading hall obsolete and a constant hassle to get it fixed. 

All villagers are kept in a capsule with methods trying to block pathfinding but all have failed. (putting them in water, solid block blocking their viewing path)