This is the one day I didn't bring my digital camera to take photos of this with. I will see what I can do in the meantime. The one that works intermittently does this whether the hotplate is on or off. Unplugging it from the wall and back in does not make it work again. The PCB with the switches has only three small resistors connected to led bulbs, otherwise it doesn't have anything on it. It is connected to the main PCB by a ribbon cable.

The units are Fisher Scientific brand, but they are a discontinued model of their Isotemp series.