Seeing the Feng Shui compass doesn't mean north and south. Why?

Seeing the Feng Shui compass doesn't mean north and south. Why? There are other magnetic interferences. Pay special attention to the following two situations: 1, the compass pointer is stuck. The pointer of the compass is shaking. In these two cases, the main family has something to do, the murder case is urgent, and the feng shui is not done well, so we must be cautious.