For some reason villagers using wrong workstations (farmer and archer using librarian workstation). It happened in Minecraft Realm
What i did with them:
Made them zombies
Destroyed their original workstations (but they already had trade with me, so they keep their jobs)
Tried to make librarian but workstation occupied by the farmer and archer, they even do work sounds, you can see it by particles.

I only have Optifine and no other modifications.