It happens to me also. I can add that my villager breeder often has more villagers of a x profession than workstations available to them. They dont loose the profession even if I don“t trade with them and a cycle passes. For me the issue started when I updated to the latest snapshot in my single player world.
Im playing the latest snapshot (19w41a) and when I break crops inside a pen with villager sleeping at night, they will slide out of the bed towards me, completely horizontal and then return to their beds