I’ve seen this sort of issue stem from an under-rated power supply on devices that use a relay to control air assist on/off. My Sculpfun S30 alpha unit had a board that reset when you turned on air assist, because it was drawing too much current from the anemic power supply. Sculpfun was quick to rectify with a new board and power supply. Perhaps you have another power supply on hand with the same plug polarity and more current capacity to test with?