I have a 7 yr old electric dryer. Last week the knob that controls cycles quit moving during cycle (this happened a couple yrs ago and cleaned out lint and it was fine till now). Now this week 2 times of use it didn't dry clothes all the way. I figured the vent needed clean. Threw another load in last night and it ran for 10 minutes and shut off. It was very hot, id say hotter than normal. It would not start up right away. I let it cool down and it did start after that but I did not use it the rest of the night. I tried another load this am and it ran but the clothes were still wet. It had heated up just fine (I changed the heating element in it a couple months ago). Checked vent which is totally clean from unit to outside. Checked the thermal fuse and it ohms fine. What could it be?