The buzzing sound and burning smell was coming from the motor. The central gearing system was jamming up in the eye / eyelid submechanism and the motor was being held locked. This generated heat, noise, and could potentially burn out the motor. (While a fire could be possible, I would guess that would be doubtful given the motor and battery sizes). The central gear system does have some sort of stroke sense switch, so I'm not sure why the software doesn't recognize that the motor is no longer actually moving the gears and kill the power (and maybe even speak out a message?)

Basically in Toh-Loo-Kah's case, the level arm which drives his eyes and eyelids was getting stuck in its cam groove which prevented further rotation of the main drive shaft. This would only happen in one spot, and only when rotating in one direction. By using a small screwdriver, it is possible to unstick his lever arm and have Toh-Loo-Kah continue, only to get stuck again next time his shaft rotates through that region of the eye cam. Toh-Loo-Kah does not seem to be able to correct this problem himself and will let his motor burn out trying. Sometimes his eye arm lever would also flex out of position entirely and end up out of the cam-track.

I did notice that his gear arm which moves his ears seems to have something missing or broken on the bottom. This may have been a piece of plastic which would help nudge his eye lever arm along in the exact situation in which it's jamming. That piece appears to be completely missing (it didn't appear loose in the body cavity during the autopsy procedure) so its exact structure is unknown. Since he jams pretty consistently with the broken ear gear arm, I assume that this missing piece of plastic helped force the eye lever arm along. I will be attempting to reconstruct this function in an effort to bring Toh-Loo-Kah back into our lives.