Hello.
I was just testing can communication with my 2 Vescs 4.20 (flipsky), which ended sadly. I connected battery to Vesc1 and connected CAN bus to it. Then I connected CAN to the second one, connected usb to it, and connected second one to same battery. I felt some smell and both vescs died 
. The 3v3 line is shorted to ground now. And the regulator gets very hot. While I could manage to resolder a voltage regulator, the mcu or drv are way beyond my skills. Is it possible that only 3v3 regulators need replacement? Do you know what mistake I made to end up here?
I've seen enough of these to know that it's more likely the STM32 micro is damaged and causing the 3.3V regulator to current limit. If you can't replace and reprogram the micro yourself you're better off getting a new VESC.
It's difficult to say what caused the failure but I wouldn't recommended hot plugging power while connected to a computer via USB.