I've run into this bug as well (Bedrock 1.12 on Xbox One). I cured four villagers a long way (hundreds of blocks) from any work blocks. After being cured, they had professions which never change. Note that I have not traded with them. I tried placing work blocks, but they will not change jobs.
This bug and MCPE-48421 have put my plans for my world on hold since villagers are broken.
Thanks Jeff! That would definitely help. I'll try it soon.