Irrational fear of letting the microwave timer reach zero. Sufferers will ALWAYS open the microwave at least one second before time runs out, thereby circumventing the ding or buzz that ensues when the timer reaches zero. The most extreme case subjects have never, in fact, heard what happens when their microwave timer reaches zero.
Frank's microwave might just play Stairway to Heaven backward when the timer reaches zero. It's a shame his microdingophobia's too bad to ever let it get to zero.