I recently ran into a bit of trouble with my Fridgidaire microwave oven. The home came with it installed as a "fume hood / grease trap" over the stove. Which makes it annoyingly hard to replace since the cabinets were positioned around it when they built the home.
Before I get into the microwave oven, there was a second problem that masked some of the microwave's issues: All six of the Eaton GFCI/AFCI breakers installed in this home are faulty. They will falsely trip showing a ground fault code via the diagnostic LED. Multiple breakers for various outlets, the refrigerator, the microwave and so on keep tripping. This is, apparently, a well known problem with early Eaton GFCI/AFCI breakers (easily identified by their extended length vs a "dumb" breaker). If you have one of these pieces of crap installed in your breaker panel, Eaton will replace them with new ones free of charge. The new breakers are much smaller--apparently they can now fit all the electronics into the same space as a classic "dumb" breaker.
Back to the microwave. The buffoons at Frigidaire decided to let people open their microwave ovens while they are running... This, of course, requires interlock switches and a relay to shunt the magnetron transformer to dampen the output sufficiently that people don't get cataracts when opening it before the timer elapses. To do this they added three switches to the door and a "protection" relay that shunts the transformer. Then there are two more relays to power the magnetron: an inrush limiting relay that uses an NTC resistor in series and the "big boy" relay that shunts the inrush circuit to fully power the magnetron.
The initial problem was that two of the interlock switches were intermittently welding together. This then caused the primary relay to weld together, which then caused the microwave oven to remain on even with the door open! Fucking nuts. Anyways, after replacing the interlock switches and eventually the primary relay (as it was damaged from the stupid interlock switches failing), the damn microwave would still occasionally trip the new breaker. After fiddling around with the door, I found out that the tolerances for the door to interlock switch contact was about a millimeter off from reliably engaging one of the lower switches... I ended up adding a strip of flexible plastic to ensure the pressure on the switch contact was enough to keep it fully engaged when the door was closed (using a good wiggle test of the handle and my DMM on continuity mode). I now believe that this tolerance issue was the primary cause of all the damaged components...
The funny thing is, if one pressed "stop" instead of impulsively opening the door, the magnetron would turn off far faster, and without all the bullshit needed to keep people safe. I think people's expectation that "I should be able to open the door even while running" is idiotic and needs to be beat out of them. The parts needed to allow this add cost, make the product less reliable, and don't make them understand that they are still being exposed to microwave radiation that can cause serious harm to their eyes, especially if the interlock system fails in some unexpected way like my unit.
TLDR; microwave oven interlocks should _prevent_ people from opening the door while running, _not_ let them open it.