Same thing here with a Kitchenaid KHMC1857BSS-1. Humming loud when door is closed. Open door and humming stops. Humming seemed like it was causing the unit to get warm. Hence I Opened door and then unplugged. Sat unplugged for hours. Did not change when plugged back in and tried. Followed the slamming of the door “trick” over and over and then voila it worked. Still a little nervous. What if it starts doing it again when no one is home? For now ok. Do I need to replace the control board? $150 isn’t bad - but finding someone to do it. Anyone else have it come back or replace their PCB ? Please advise.