After just over 2 years of use, the lower interlock switch failed. I replaced it with the same type of switch (I used a 3 terminal Omron D3V-16G-1C25K (16Amp) in place of the 2 terminal (N/O and Com contacts only) 16Amp Omron D3V-16G-3C25K that failed). Two months later, the switch failed again. Then just after two days of use it failed again. In each case, it is the N/C terminal that gets hot and melts down the plastic case under the terminal, ultimately opening the contacts. (An earlier Kemnore microwave also caused these switches to fail in the same way (though not as often) so I had a supply.) Any ideas as to what may be causing this failure? I've checked for shorted transformer primaries, secondaries and magnetron filaments, and found no obvious problems there.

No, I haven't replaced the terminals yet. The one that connects to the overheating terminal is the white lead that goes to the transformer primary. The white insulation on this lead is a bit discolored so I suppose replacing the terminal might be worth a try. Thanks.