villagers can sometimes lose their profession by being too far away from their job site even if the job site isn't obstructed and the villager can walk to the job site.

sometimes i would find a unemployed villager in my walled up village and i checked that every villager has a job. For example, this happened to one of my farmers. the title explains the rest. Recently, I found out that this happens with beds. This makes the villagers not go inside any building, and that results in them getting killed by zombies.