I have a Roper RED4640YQ1 Dryer. It does not complete the drying cycle on either Automatic Dry or on Timed Dry. On Automatic Dry the timer doesn't move at all, however in Timed Dry the timer will advance all the way down to the "cool down" section, but it never advances past this point, the heat doesn't shut off and the dryer will never stop until the door is opened. What likely needs replaced to fix my dryer? I know it's not the START button, I'm thinking it must be a sensor of some sort.