Could it be as the motor is straining with achieving proper torque that it is trying to draw to much as thus over-loading the coil? I know that this is only a 12v DC motor, but the thing is geared up even after that for a lot of torque. I am wondering because of the gauge of wire used, if that wasn't engineered as a sort of dumbed down thermal fuse of sorts and hence the thermal wire sleeve? If that be the case it would be sort of really dangerous in its current application. But, that would be Chinese engineering. Further research into this has proved that at some point the company was made aware of the unit's tendency to over heat and over-draw. I could not find anything on the circuitry of the unit as it is probably a state secret and property of the Chinese Government. The new motor seems to have greatly improved with better brushes and even a built in cooling fan to boot!
I am looking at the following as a replacement. But this is where I know absolutely nothing about loads or etc and look to a community of experts and/or subject knowledgeable peers for help.
40uH 20% Axial RF Choke Inductor RCW0520U-400M-032-L
https://www.westfloridacomponents.com/IN027/40uH+20%+Axial+RF+Choke+Inductor+RCW0520U-400M-032-L.html
I am not sure where my endearment for these old machines, tools and other widely collected/hoarded items comes from.
Or why I have become strangely fixated on fixing this thing, when I probably could have scrapped it and bought a new one for less then 200$. And saved a week of researching, but where is the challenge in doing that?
Nothing ventured, nothing gained. Plus I would rather spend $0.66 and burn the windings or the board up then say I didn't try....
Just realized that coin above say In COD we trust... Love a good game of Call of Duty. And speaking of duty.... just realizing now that 20% for the choke may be referring to a duty cycle....