Howdy,
I don't know if I should cry or yell but this whole story seems very surrealistic to me... I'm just integrating replacement solution and opened also "still working gears" in order to replace the control PCBs: And wholy crap what I found!
Damn Airtech Germany sold me some prototype stuff!! ALL 3 controllers are different kind. please refer to the picture: two with solder mask but different kind of FETs and one PCB has not even solder mask! ie. probably from the very first proto round. (which I find kind of odd as I don't know any good reasons to omit solder mask with today's PCB prices...)
Also while testing the replacement solution I found out that the sensor magnet of the failed gear was totally dead! So this means that the controller didn't get any pulses and it had to rely on current limit to stop at the end. In addition to very questionable HW design it might be that the root cause was actually the broken magnet and then current limit feature was not working correctly and whole thing burned. Just guessing (as the motor survived...) Airtech Germany claims they test everything but it's fairly difficult to believe... Be careful out there if you are using their stuff! They apparently sell expensive untested prototypes without warranty.
And last but not least: one capacitor on the "proto PCB" has been totally destroyed while soldered or handled. This gear was working though:
Now I also know why Airtech Germany dude got angry when he heard I opened the case... He didn't want to reveal what was sold.
I will update you soonish about the improved replacement solution.
Ilkka