Same problem with middle 'monitor' micro switch where the contacts on the inside of the switch become welded, tripping the breaker and never working again. My GE microwave is a similar model, the micro switch is a KW3AT-16 (GE part# WB24X10205), normally closed. Bought new, just over two years ago. I called GE's Relations Dept and pointed out that this issue shows up a lot when searched online for GE microwaves. They sent me replacement switch ($40+ value) for free, which was very kind.
Unfortunately, within a couple days, one of the kids popped the door open before hitting cancel/pause, causing the contacts on the new switch to weld again. I suspect (like the OP) that it has something to do with the door alignment on the main upper and lower switches.
What I'm trying to figure is how to find a suitable replacement that does not cost $40.
The original KW3AT-16 switch has these specs:
16GPA 125/250 VAC 40T125 5E4
1/3 hp 125VAC 10A 30VDC
16(4)A 125/250VAC 40T125 5E4
10A 30VDC 40T125 5E4
I am considering replacing it with a similar sized switch with the following specs (Amazon, two for $13.50 shipped) :
0.6A 125VDC 0.3A 250VDC
16A 1/2HP 125/250 VAC T130
16(3)A 250V ~ T130 5E4u
I'm not sure what all these specs mean, but it seems that the second switch can handle 16A vs 10A, 1/2HP vs 1/3HP and similar resistance (5E4)... Or perhaps I've got it all wrong
Any insight into how to compare micro switches would be greatly appreciated!