I have this system. I bought it new, and it had the problem day one. I contacted Jim Bartell and Don Wetzel of Loon Works whom makes the M-One Motor.
Immediately Don Wetzel knew the problem. The potentiometer inside the motor is the ONLY part that is wearing it self out. The only part in the entire assembly which Don states no matter how expensive or well manufactured the individual fomponent is, which he states he is using the expensive best made part...
it will wear out eventually, and it doesn't stop working, it slowly starts to intermittently fail.
The ONLY way to remedy this annoying wiggle squiggle shaking of the motor ... this random minute but loud and noticeable vibration of the motor back and fourth attempting to lock onto a stepper position is to replace the potentiometer.
So... As long as the unit is beat up on the outside and looks like you've cared for it... for the most part, don't quote me... but if it is a fairly recent purchase and you pay for the shipping to MONTANA where LOON WORKS and Don Wetzel are located,,, he might replace it for free..
He did for me.
Guarenteed to solve your problem!
I just wish I had contacted Don long long ago and saved myself the issues on set, the AC's not sure of the devices reliability or performance.
Let me know if you have any other problems.
Contact LOON WORKS DON WETZEL Montana. http://www.loonworks.com