That looks like the buck converter burnt out. Makes sense too, taking 42V at continuous discharge of 80Amps (more or less if defective BMS, also based on my readings here) and outputting anywhere from 3-12V would result in a ton of heat buildup. Might solve it by adding a precharge mechanism to absorb the initial discharge (bigger caps?).
They’re using the STM32F4 series it looks like, but not using a gate drivers I recognize. The VESC for comparison powers itself from the on board buck converter (like above) but could also get its power from the DRV8301 series gate driver (currently floating).
I would be interested in seeing if the VESC would be more compact and reliable if the main supply to the STM32 came from the gate driver.
If you’ve got a moment, I would love to inspect the board and see if I can give a repair write up for people looking for out of warranty repair solutions.