While creating a villager trading hall, multiple villagers linked to one smithing table, grindstone, and blast furnace at once. Unsure if intended or not as a feature but can cause issues for villager halls on servers and singleplayer worlds.
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Yes, multiple would link to one station and they'd be stuck in that profession, I tested more on my test world, those seem to be the only blocks that link with multiple villagers and the villagers don't lose the profession.

Duplicates MC-152182?
Did you break and replace their working station?