I hate to be the one to say it, but I bet a lot of us are thinking it right now: there may be a fatal design flaw in the actual hardware of this unit. The motors (particularly the one that handles the roll compensation since that one is 90-100% the one that starts squealing first) almost seem too small or weak for the task assigned them of keeping the GoPro level. How did I come to this conclusion?
When the quad is powered up and hovering in place, or sitting on your workbench and powered up for NAZA calibration, the gimbal is leveling itself out and holding the same relative position for long periods of time. The motors make a low humming sound just to keep this position, indicating they have to work to achieve it. So it's no surprise that the motors squeal/burn out in this exact same position as is the case with almost every gimbal that has started squealing within the last week, including mine. Roll the quad, gimbal goes quiet, level it out, and the squealing starts.
If mine wasn't already sent back to the dealer, at this point I'd say if you just received yours, I would definitely hold off on an install/power up until we get an official word of acknowledgment from DJI, or a main NAZA/PMU firmware update above ver 3.14 that may change the frequency response of the gimbal motors. That is the only thing that would change my mind on the matter.
From what I gathered with my gimbal, once it starts squealing, the hardware is already damaged and no software/firmware update is going to fix it. Reading through the change log for the new update to the IMU/GCU, it introduces a new hibernation mode so the motors don't burn themselves out, but I don't see how this is going to fix gimbals that are already squealing from damage.