Problem shutting off vanguard engine

Hi Everyone,

Having an issue with one of my vanguard engines on a snapper walkbehind hydro.

When the key is turned to the 'off' position, the engine runs very slightly rougher, but doesn't shut off. I ruled out the switch itself, by touching the two wires that go to the switch and the same happens. Im not sure where to take it from here?

Thanks.