The top door switch starts to fail.
I am also experiencing a similar issue. The top door switch starts to fail. At first the turntable and cooling fan continue to run if the door is open. (They are normally off with the door open) Then shortly thereafter, when attempting to cook, the magnitron will not work but the timer counts down like normal. The top switch is not melted but it appears that the button return spring has failed and the switch is stuck in the closed position. I'm about to replace this switch for the fifth time.. Good thing I bought a 12 pack from Amazon!. Any thoughts on the root cause of this issue?