Pedal buzzes unless a buffered pedal comes before it

I built a Paragon with some mods and the thing buzzes on bypass and it gets worse when a foot switch is on. I've confirmed all board components are correct, I replaced all off board components and wiring, I changed guitars, amps, speakers, and cables, but no matter what I do the thing still buzzes. I assume it's some grounding issue but for the life of me I can't find anything that would cause this.
When I used the pedal with another pedal before it that has buffered bypass, the buzz goes away, even just a tuner works. It still buzzes with a true bypass pedal before it.
I'm curious what would be causing this and if there is anything obvious i.ahould be checking or changing to mitigate the buzz.
Thanks all
 
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