The foam CTE moving the resistor does make sense. I would have bet money there wasn't a sensor in there. Hopefully their digital controls are better, it would be nice if they had a calibration feature. I think I will stick to the $16 aquarium controllers.
I am just finishing up a hatch with a little giant 10200 (forced air, manual temp adjust) with so so results. I think i have traced the problem to the manual "thermostat" not being a thermostat at all, but merely a timer circuit. Most people remedy this by keeping the room temp stable, therefore...