Villagers stealing job level progress

I had several villagers who were not locked into a profession. I took a stone cutter and traded some clay with him for emeralds to lock him in. He became level 2. Then I broke his job block to move it because it was causing congestion, and when I placed it back down he was back to level one, as if I had never traded with him. Then I went to trade with an armorer (whose job block was underneath the stone cutter prior to me relocating said stone cutter block) and he was level 2 just like the stone cutter had been.