On 19w14b a shepherd claimed a smoker as a work station instead of a butcher, although he does no work, and just stands there. there is another shepherd in the village who actually works at a loom, the only loom in the village. 

In prerelease 1 I went into a creative world and spawned a villager next to a smoker with no other villagers or workstations around, and the game crashed with this error message:
The game crashed whilst ticking entity
Error: java.lang.IllegalStateException: POI data mismatch: already registered at ev{x=95, y=63, z=-401}