I'd bet a dollar that the internal spacer tube the the magnet on it is rotating with the wheel causing the PT to think it's stopped moving. The trick to the PT bearings is seating them tightly enough to that the tube is held in place by the inner bearing races and not spinning with the hub itself. The magnet on that tube it what trips the electronics to come to life and is the index for the wheel revolution calcs. Either that tube is rotating freely or the taped on magnet is loose. At least those are the simplest options.