if you have removed the tone control, both sides, and still have the problem then it is not your tone control causing the problem. if you have removed the ground off of the 5 way, and still have the problem, it is not that as well.
we know the circuit works, but the problem lies in the effects loop when engaged. we also know that when the effects loop is engaged, the send side is working. so we need to focus on the receive side of the effects loop.
i need to see some pictures of the wiring.
"The process of selecting the tone on the guitar is an aesthetic process like any other, so you try a lot of different things. Most of the things I’ve tried I’ve tried in live performances" ~ Jerry Garcia