I just fixed one. The door monitor switch is the prime suspect, BUT not the only thing. If that switch is not activated when the door is closed it puts a direct short across the AC line, which is what trips the breaker, but it does not blow the internal fuse. The problem can also be caused by worn out plastic assy. that holds the switches allowing the activator to drop too low and not trip the switch - as it was in the one I fixed. You need to verify that the switch is functioning or not, then look closely at the area the activator rides over. If it looks rough and worn, it is a $35+ part. The switch is also being scammed for the same or more, but can be had on AliExpress for about $5.