Cvc-168 vending issues

I finally got to look at my CVC-168 again.  Of the 5 Vending Mechs I have one that still works (The double sized one on the RIght end).  the first 2 on the left side won't vend from the button but when I push the Manual Feed button they do turn.  Any Ideas?  Could it possibly be the Switch in the door?  If so where can I get one to try it?

Thanks again...

Todd....