I don’t know if it is just my FA pro stick II, but it is very touchy to movement while connected to USB port. The slightest movement of the dongle causes FA software to reacquire antenna and MLAT. Has anyone used like RTV or silicon to “weld” it to the USB port to keep it from moving?
I had this exact problem from day one with my ProStick Plus and Pi4. My solution? Put a small square of masking tape on one or both sides of the stick’s USB connector. It was enough to provide a snug fit and have had no issues since then.