Microwave door interlock switch keeps failing
So I noticed on part 125 the latchboard the latch "ramps" appeared to have worn down a bit which might cause the switches to not all flip in the appropriate sequence.  So I purchased and installed a replacement.  

When I installed the new latchboard (and new relays) I made sure the latchboard was firmly screwed to the frame.  It's possible if the latchboard was loose (I need to unscrew and remove it to replace the relays) it might also cause problems.  

I did this mid-November and thus far we've had no more blown fuses.  So fingers crossed!  I will edit this answer if the problem reappears.