Everything works fine, drys fine, except that when I want to get something out early or check the clothes and open the door the dryer keeps spinning and doesn't stop. Is there a sensor or knob stuck?

Sounds like the door switch is stuck closed. Push in and out on the plunger and see if that releases it. If not remove switch and check the contact on it. If bad replace

There is no switch that I can see there is a metal piece that sticks out and a slit on the door that it goes into when door is closed