This is a weak point/design flaw in these microwave ovens - all brands (residential, too). The part of the internal latch mechanism that holds two door switches wears and the switches don't make/break contact at the same time. This blows the internal fuse. You can keep replacing the fuse until the cows come home, but it will keep blowing. Depending on the microwave brand, you can order a replacement part (the old switches should be fine). The Frigidaire part fits our Furrion microwave/convection oven, so I have a spare on board.
Rob