I'm not sure why is this happening,but I have been having an issue where a villager doesn't recognize their job site. I had this happen to a Tool Smith and a Librarian. Whenever I break their job site and place it back down then put the librarian next to it another villager takes the job and the librarian acts if they are unemployed and starts wondering around.
Linked issues
Comments 2
When you break the job site block, it no longer belongs to anyone. The next villager in the village waiting list, not the closest villager, will get the next job site you put down. This is working as intended per MCPE-45270.
Minecraft wiki
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it is normal behaviour for any villager to take any job if they don't have one