You could test one section at a time. Pull the tail belt drive system and main gear out, test just the motor. Then add the main gear and test, add the head and test again, add the tail drive section test again with no belt connected. Working your way back you should be able to narrow down what it's coming from if you test each part incrementally.
I can't say that I've noticed anyone's Synergy with a strap over their vbar sensor.