I replaced the start switch with AP2975191. Wiring it as shown on the wiring diagram (black and white/red), the dryer will start for an instant but not stay on. The switch has 4 terminals, but the wiring diagram shows only those two wires being connected. I have a tan wire that is not connected, and another black wire that comes from a different component (not the same origin as the black wire coming from the bundle, and I can't identify this small black component on the wiring diagram). I have no idea how it was wired before because I had tenants who tried to jerryrig some other switch after they broke the first one. I would appreciate any help!

That's the wiring diagram I have. I have wired the switch as shown. Now the dryer will come on, but it won't stay on. If there's a tech sheet for troubleshooting, that would be helpful.