I suppose there is a sizzling location close to the back wall. I believe it's radiant warmth in the steel the place the chambers are linked. One particular Answer that seems to help is I hold my fireplace from the back of the fireplace box and nearer for the lid https://kitchenaidcartstylecharco51358.activoblog.com/14275248/new-step-by-step-map-for-over-and-under-smoker