Older Gas Dryer Only Pushed Heat When Buzzing

Our Kenmore gas dryer, which is a bit old, recently stopped producing heat. We replaced the heating element, but after reassembling everything, we noticed that the drum only spins and stays lit when we hear a buzzing sound. It appears that if we turn the setting knob just a little, we get the buzzing and heat. I suppose it's this particular knob that needs replacing, but I wanted to see if anyone has any insights on this issue.