It sounds like what happened the other night with my one rack. The herpstat woke me up in the middle of the night going off because the temp was too low. But when I used the temp gun it was around 120-130 where the hot spot was supposed to be. The probe had slipped off which made the heat crank up to try and reach the right temp. So I had dangerous temperatures even though the herpstat thought it was too cold and it only seemed to be getting hotter in there before I figured out the issue