Ebay Seller Who Awas Refunded Wants Product Back

Location: NY

Purchased an item off eBay from someone in MA. the product was missing a component that was not disclosed and I submitted a return request. After some back and forth the guy approved the return but then said he'd send me the missing piece, which he did. In that time the piece was shipping he sent several harassing messages and I ultimately decided to proceed with returning the item to avoid dealing with this person further.

My mistake was letting him know I would be returning the original item and separate piece back to him together using the eBay return label. He then immediately opened a dispute case (which cancels the return process and deletes the return label) with eBay which was promptly ruled in my favor. I was refunded and was told that I do not have to send the item back and that the seller kept the sale price.

Today I get a certified letter from the seller saying that although eBay let him keep his money he is still the owner of the item and I need to send the item back to him or send him money for the purchase price, or he will go to small claims court

Feels like more harassment and intimidation tactic to get more money. I spoke with eBay and because this is outside eBay communications they can't get involved at this time but confirmed he did get to keep the sale money and I do not need to mail anything back. ebay will not send me written communication confirming this, but kept referring me to the purchase status page which says case closed in my favor no further action.

Since this is through eBay don't their terms govern? What recourse does he have, if any?

thanks all