Originally Posted by
sharkey00
Try cleaning the magnet and sensor.
Don't think that will matter too much since they're magnetic, but I would align it better and tighten them both. The magnet has to come very close to the pickup for it to register.
If the magnet can rotate at all on the spoke or slide a bit, you can definitely get dropped signals.
The battery could also affect reception, but I'd fiddle with the magnet first given the symptoms.