When I bought a Surface 604 from Cal's Cycle in Linden AB, there was a problem with the sensor but they obtained one from another in stock. I purchased the new one in case there was an issue and had it installed at Power in Motion just to be sure it would work. It seems to be working well except on level 2 and 3 on a slight incline where the power seems to be intermittent. That is, it feels like it comes and goes which is not what I expected. Can you assist? Thanks