Stutter Box - need help!

Hey eveyone, just throwing this out to you guys hoping I could get some help.

I'm building a "stutter" box for a friend. He needs a a box that can act like a piano key, when the momentary switch is pressed, you hear the guitar, when he lets off, it is silent. Also, he needs to be able to bypass it and allow the signal to pass through.

I built this and it works:

It does exactly what he needs, but when I install it in a metal enclosure, the input jack shorts it out or grounds it and I get no signal. if I remove the input jack from the enclosure it works fine. Is there a way to wire this thing so that it won't ground itself, or do I need to just find some plastic washers for the input/output jacks?

Thanks!