I've got about 100 miles on this bike. Today the assist started cutting out with no apparent pattern. Was constant for the first six miles or so and then returned to working as expected for the next six. Fully charged battery, cadence was 70 to 90, level ground or inclines made no difference no matter what the assist level. Latest firmware installed, sensor magnet is clean, fazua toolbox and mobile app show no faults. Anyone with any ideas?