mwaves have 2 common problems, push on connectors and door switches. If an internal fuse blows, the problem then becomes a magnetron power supply or magnetron issue. And yes, replacing/repairing any ot that requires removing from wall.
Push on connectors get loose and heat up, burn insulation and wire covering, then stop working. SSo they are very obvious when looking at them. Switches become misaligned or also burn up especially if doors are opened while operating.