Wow, that's really surprising! He should have returned it right away bc ZooMed warraties that reptibator for 1 year and it's a 100% one for one if the PROPORTIONAL THERMOSTAT is found to be defective. I am going on my third season with no problems at all.Maybe his temp fluctuations came bc he was using different tubs to incubate his various clutches? You take the lid off and it depends on how long the lid is off and what your incubator temp is set at? I don't keep the lid off for any extended period of time bc i know it's important to gather your equipment and be prepared to do what you have to do to minimize the time the incubator is vulnerable.