Add On Top Boost - grounding loop??

[12strings]

Hi, I installed an add on top boost unit to a vintage ac30 per the 60s add on top boost schematic. It sounds awesome. However, when the brilliant/top boost volume pot is turned all the way down, I still get some bleed through guitar signal. I also have the normal, vib pots on zero as well.

Do I have a grounding issue or is it an issue with the brilliant channel volume pot? I grounded the top boost unit to tab at V1.

Thanks in advance!

 

[Masco]

That's normal.