Engine run-on... Fuji 32EI

I have a Fuji 32 EI on my GSS and it flies extremely well. However, I cannot stop the idle with my trim tab. The throttle is completely closed but it still runs on ....
It is an extremely low idle but it still will not stop idling until I flip the manual kill switch. I do not have a remote kill but it should still stop with the throttle closed.
Does anyone out there have any experience with this kind of issue. The Fuji 32 EI is new and I have just finished running about a gallon through it.
Please advise

thanks in advance