Cavalier machine not preventing vend

[Clackboy]

My Cavalier 1USS (old machine) is not locking the rotator mechanism after each vend. When I put money in, I can hear the solenoid "kick" to release the mechanism, but after I rotate the selector to dispense a can, the machine doesn't reactivate the mechanism to prevent taking another can. The machine is not set to "free", and all the other slots seem to be properly positioned. Thoughts? (I am handy, but new to vending machines.)