The bug

Villagers already skilled in profession (i.e. apprentice, journeyman, expert, master) but without job site do not get precedence over unemployed villagers when a that job site block becomes available.

Because "skilled" villagers do not lose their profession, this can lead to an unemployed villager being assigned that already has a "skilled unemployed" villager with that profession.

These villagers are unable to trade further once trade cap as they do not have a job site block.

Ideally, when a new job site block becomes available it should search for any "skilled" villager which does not have a job site block assigned before assigning to an unemployed villager.

How to reproduce

1. Create or find a "village" and have some unemployed villagers
2. Add a job site block (this should now be assigned to a villager)
3. Trade with the villager until they are "skilled"
4. Destroy job site block
5. Add same job site block in village
   → This will now be assigned to a villager, this could be an unemployed villager instead of a villager already skilled in that profession