Buyer requesting refund on item they haven’t received yet - parts only sale, no refunds

Buyer requesting refund on item they haven’t received yet - parts only / no refunds

1 hour after I delivered item to post office to shipped out, buyer requests refund request thru eBay. I declined refund since item is FOR PARTS ONLY and listing stated no refunds. It appears refund has been closed in eBay app.

However Buyer messages me still requesting refund stating they thought item was working so they are still requesting refund.

**Had the item NOT been shipped, I would have refunded. Asking for a refund on an item they had not yet received, really seemed like a scam to me. So I kept with no refund as stated in listing.

The last text from the buyer stated “I'd still like to return this item, since it's not in my possession yet, the revivers would be notified and it would be returned to you” and it sounds like there is a 3rd party involved (revivers) that’s involved in the transaction and not sure how that will work on buyer potentially getting eBay to reverse my no refund.

What do I need to do to protect myself from buyer reopening this and getting eBay to issue refund?

Item and buyer screenshots included.