I'm not sure if the incline restriction applicable to my TC-Max also applies to your bike, but mine will cut-out when exceeding a 16 degree incline (uphill climb, according to the manual). I have not experienced this on the roads where I ride, although I did half-expected it to happen while riding through one particularly steep hill. However, I did experience my bike cutting-off while positioning my TC-Max to ride over a steep ramp of a motorcycle platform lift. I had to start again from flat (garage floor) and sped up a little bit more to gain momentum so the incline restriction didn't have enough time to activate.

But you mentioned that you were only traversing "slight hills" so it might pay to have someone check if the inclinometer sensor on your bike is faulty. I actually don't know where that sensor might be or how it even works, but one can only assume that there must be a sensor somewhere. If the inclinometer is an external unit (just a guess), I can imagine that it might behave as you described if it got accidentally nudged out of it's normal horizontal position.

I would be interested to hear back about your findings - if you have found the cause and a fix.