I've not found any issues with the board. I went ahead and clean the cart slots and replaced 2 damaged feet.
Your audio issue may just be dirty carts. This is what I normally tell people
"You dont need to take the carts apart to clean them.
Wet a q-tip with rubbing alcohol and go in/out on each of the pins of the cart. I usually use 1 q-tip end per board side. The pins may look clean, but you will find the q-tip will turn black from the oxidation getting removed from the pins."
Unless there is something else you want me to look at, i'm ready to package it up and ship back. I still can't seem to PM you on here, can you msg me your shipping address on ebay.