Been
Selling on eBay for 15 years never had anyone do that, as long as you take photos of your serial number your safe?
Plus once positive feedback is left there’s nothing they can do PayPal won’t do anything as it’s through eBay not PayPal
Just use google to search, hundreds/thousands of sellers have been hit by this.
If the buyer uses paypal to pay (which you have no control over) they can get a refund no matter what, within 6 months.