Mine has been warped since the first year of cooking 8 years ago, but keeps getting more twisted. Replaced the controller with an Ortech a couple of years ago and have been very happy with it. Last few cooks monitored with Tappeque have shown some really high spikes after a few hours. Ortech Tech Support sent a new RTD, same results. Looking at the heat shield again, it's raised up 1 1/2 in. or more. Always read that this has no effect on temps, but after replacing it everything back to normal. Temps are + or - 15 degrees. Could it be too much heat escaping on one side or another, I really don't know.