thin metal and cheap construction makes steady constant heat hard to achieve. The fluctuations are pretty dramatic. Even the best smoker traeger makes doesn't hold up to the "real" smokers.

One thing you can do is to get a wool surplus blanket and put it over the cooker while it's smoking. It will stabilize the temps and help it hold heat better.

or - you can do what I did and get sick of messing with it and buy a better smoker. I have a Yoder and it's bomb proof, but there are quite a few brands that build great units. Thick steel and a much heavier duty construction equals much steadier temps and easier to achieve results.

Lift the lid on a treager and then on one of the heavier duty units and you'll see the difference.