Backfeeder background static noise

I am working on my second backfeeder. The first one no longer produces feedback (I had to replace a component and I think that damaged the pcb.) Now my current build, there is some static in the background and is mostly heard as the note decays and the guitar volume is quieter. It does this whether it's in the enclosure or not. I've already replaced all transistors, op amps and IC's. I also replaced the potentiometers and bypassed the footswitch. I feel like I've eliminated possible hardware issues. I checked all my values and soldering. Happens at low or high gain sounds. I've built the defouler (just the distortion side) with no problems. The other board I was working with, the distortion is fine. It sounds very similar to the occasional static with silicon fuzz faces, but adding a capacitor across the transistor collector-base removes the sound. It doesn't sound like radio signals either. I truly don't understand what the problem is. Has anyone come across this? Thanks.