New pedal sounds great but squeals if I turn guitar vol to 0

[rfdvrcasey]

I threw together the Snack Shack fuzz pedal that Madbean threw in as freebie.  It sounds great when playing but I noticed that when I roll the guitar volume below 1 1/2 the guitar sound drops out and is replaced by a squealing tone that is constant in volume and pitch.  I don't hear anything unusual when the guitar vol is set higher than that.  Any ideas where to begin troubleshooting?

[JackSkellington]

I don't understand what exactly you did, but I got a similar issue with a Big Muff DIY clone. I messed up with a ground wire.
Try to check the grounds spots in your board, in case you missed something.