Thanks to Chris and Phil for the great info on how to get at the circuit board! I checked all four switches with a multi-meter, and all but the bottom ‘frozen’ button were flaky. When pressed the resistance should be steady and near zero, but the resistance readings on the upper three when pressed bounced around and were not near zero. This leads me to believe that the problem is environment (heat and moisture) rather than mechanical wear, as I never use the F/C button and rarely the convection button. This also means that swapping switches is not likely to lead to a long-term solution. Here is a link with a bunch of switches that will work (don’t get the ones where the picture shows very long legs) : Switches from DigiKey. This one, Best switch has gold plated contacts and is made for corrosive harsh environments (It is also vastly more expensive than the others, but still only $3 each)