Sometimes the scene with Deor and Fanari talking about the missing smith doesn't complete.
They get stuck, keep facing each other forever, and you can't start the "A New Source of Stalhrim" quest.
If the scene fails, asking Fanari 'Did I overhear that someone is missing?' starts the quest, and they can go back to their business.
If the scene doesn't fail, this just sits there and does nothing.
If you don't get the bug you don't need the fix, of course, or you could just keep it as a safety valve, your choice.