I am not a Tech, just a guy that likes fixing stuff, but your description of the problem makes think of the door safety shut off switch. The fact that it can shut off at anytime, but especially after the soap door opens made me think of this. The models that I know make a snap or clack sound when the soap door opens sending a slight vibration thru the door. If the door switch is barely making contact that might break the contact. If you remove the inner door panel and access the handle, the switch is probably in there, maybe a reed type switch that could use some cleaning or tweaking at the contacts. Just an idea, but your listening to a guy that fixed his VCR by putting maple syrup on a drive wheel.
Good luck, Key