On a rare occasion somehow this thermocouple has fallen out of the silicon collar holding it to the heater. Because the thermocouple is not touching the heater, it can not read the heater is getting hot. When this happens we will have to replace all the inner guts as it has more than likely overheated. Bottom line is that if the unit is doing this, the customer needs to return it to us to fix. You can see in the picture that the thermocouple is out of the silicon sleeve. We will cover shipping both ways for this scenario.