I'm playing in 20w19a, and villagers simply won't lose workstations. All possible workstations in their area have been broken, they haven't been traded with, but they still retain their jobs. However, this issue is highly inconsistent - before I had issues with three villagers not losing their workstations, then one of those ones did lose their workstation, but now all of my villagers are stuck as librarians.

Again, there are no other workstations in the area - no barrel, no lecterns, nothing - and they have NOT been traded with.