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?
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.