We bought our kitchenaid microwave new 5 years ago. never had any issues with it. Last night we microwaved some frozen tater tots for our kids and noticed smoke coming from the microwave. a single pea sized spot on one of the tater tots was very burned - there were no flames. the tots were about 40 seconds into a 1 minute heating when we cut if off. we decided it was something with the tots. maybe some plastic from the bag stuck on one and we didn't see or some other material. also, we used the same paper plates we've used for years if that helps any analysis.
today we were microwaving some leftover chik-fil-a nuggets from lunch, again on a paper plate. we noticed smoke again coming from the microwave and a single nugget was beginning to burn with a pea sized black spot. these were left over from lunch so there couldn't have been any plastic or packaging stuck to it. my wife set the timer on the nuggets for 16 seconds and took them out after only 8 seconds due to the smoke. so whatever is causing the burning is doing so very quickly.
between these two incidents we'd used the microwave twice with no issue.
im not sure if it's a coincidence or a problem with the microwave - if so what would cause this? its almost like the waves were superconcentrated on a singular spot both times, but again, we used the microwave twice between incidents with no problem.