Hi, and thank you for reviewing the Timberline XL. Although all pellet grills can be expected to fluctuate a little due to the way they work, swings of up to 30 – 40 degrees are certainly excessive. Unless you are using the Super Smoke feature, which is more about maximizing smoke production than precise temperature control, the range should typically fall within 25 degrees in either direction, with the average still being very close to what the grill is set to. But if these extreme swings are occurring during normal cooking, then they should be correctable without much effort. The most common causes for this type of behavior on the new touchscreen versions of the Timberline (and Ironwood) are often related to an improperly installed firepot, outdated firmware, or using foil on the drip tray. However, if these have already been checked, or if you would just like some help checking them, please give Traeger Customer Service a call. One of our agents will go over everything mentioned above, and even some more unlikely possibilities if it turns out to be something else.