Yep the same for me,I need a bigger front sprocket to get any faster,Turning the sensor and using a magnet is still working fine even with updates and no error
I just bought a disc magnet, stuck it with silicone to the crank arm and turned the sensor been fine for the last year with no errors,cost about £3.You will not get more power by using any electronic boxes,all they do is remove the 16.5mph power assist cut out