Appear to have fixed it. Unplugged oven and took apart the clock/control board off its holder (be careful of the plastic tabs that hold it in place) and to pull off the knob from the shaft for adjusting values. (Be sure to touch the oven metal first to dissipate any static charge you have on yourself so you don't zap the board... assuming it isn't zapped already) Used CRC electronic cleaner on the plastic slides and around the pushbuttons on the front panel working them in and out until they were totally clean and free to move (years of accumulated grease apparently were making them stick and hold the switch closed). Make sure all the front panel pushbuttons and slides are totally retracted (ie fully forward on the control panel away from the control board) and reinstall the board, again making sure all the plastic tabs that hold it in place are seated. Just make sure you turn on the power and make sure all the switches still function before sliding the oven back in place, otherwise you'll have to take it apart again like me! Hope this helps someone.