Paypal claims are a separate matter from eBay. The buyer can start a Paypal claim up to 180 days.

If the buyer has opted into Paypal's offer of free returns, they get the return shipping back from Paypal...won't cost the buyer a cent. If they return through a Paypal claim.

If you refund the original payment once you get them back, with no claim, the buyer will have to "foot" the return shipping if they agree to return to you and you refuse to pay it. Keep all emails saying who agreed to what.