i feel for op as i went through a similar situation. i sold a pair of foamposites on ebay last month, the soles were separating. i clearly mentioned in the listing 3 separate times that there was sole separation and i recommended them getting re glued. i mentioned in the listing to ask any questions prior to purchase to avoid any misunderstandings.
buyer gets the shoes and complains about said separation and demands either a $25 partial refund and keeps the shoes or a full refund where i cover his shipping, i told him no, and that the auction was clear. he filed a not as described claim. i messaged him telling him to cancel the claim and he was overly defensive talking about how i was making threats to him. put his paypal email in the search section on fb and found his fb which had his place of employment, his mom showed up on his friends list and her job was on her page as well. called him at his work and told him i was going to get him fired for fun if he didn't cancel the claim. he told me to screw off and that he was calling the cops. sent a few complaint calls, put the work in to get access to the higher ups at his job, sent a few emails and a few days later he canceled the claim.
you gotta be as specific and upfront as you can be when listing used shoes, but its lame how a buyer can have the full info on the item there in front of him in the listing where everything is upfront and made clear to the buyer and he can still file a claim or chargeback.
op inbox me all the buyers info, i'll try to get as much as i can on him and his immediate family for you. i guarantee you a call to his moms job will change his tone up quickly