Buyer returned opened item

[super-dude]

Hey all, I'll make this as simple and to the point as possible. Buyer purchased a sealed Dreamcast Web Browser for $149.99 then opens it and tells me it has a disc read error. Even though my return policy states that an item like this must be returned still unopened (because it's a collectible and opening it greatly decreases the value) I told the buyer to send it back and I would either replace it or give him a full refund if it didn't work (IF) ..so he sends it back and I pop the disc into my Dreamcast system. It works. I try another Dreamcast system, it works. I try another Dreamcast system just for fun, the disc works again. Now I'm in the middle of a claim that the buyer opened calling me a liar and saying I want to rip him off and keep his money and that he's going to ruin my good name to his gaming friends on FaceBook yadda yadda yadda. I checked his feedback and here's the information I gathered just from reading his feedback for the past 6 months. He's received 7 refunds, 1 replacement, claimed 4 items didn't work, left 2 Neutrals, 2 Negatives and left 7 various complaints out of only 73 transactions. That is ridiculous. I haven't had that much trouble on eBay in the past 2 years (probably more) and I'm involved in many more transactions than this guy. Obviously he's been winning these disputes as he's happy to share it in his feedback. Sounds like someone abuses eBay's buyer protection and the good will of sellers to get stuff for free. I'm awaiting eBay's decision before I continue with anything. I told the buyer he should take the disc back because it works but no, he tells me it doesn't work. I'm thinking he kept the sealed copy and sent me a used one back or maybe he really did open it and just made a copy of it. My question is this, do you think he has a legit chance to get away with a scam like this? Like I said, he obviously has in the past ..frequently.

His claim is that the item is defective but when I tested the return it is fully functional. His claim is false.