In Feb I bought an IWC watch which went through the ebay authentication process and passed. I then decided the watch wasn't for me and sold it in April, also on ebay and via ebay authentication which it passed.

10 days later the buyer messages me to say they aren't happy, they've taken the case back off and the serial number doesn't match and they also dispute some of the markings on the back.

I explained that i also bought it on ebay and used EA which means it has passed it twice so he must be wrong. he messaged me again arguing his point so I said it was now between him and ebay, and he subsequently raised a case. A week goes by and I now get an email from DPD courier notifying me of the ebay return delivery. When I checked the order I can see that is indeed being returned to me following authentication. I'm very confused now and slightly concerned - confused in that it had already passed 2 authentications and concerned. given i had already received the funds and withdrawn them.

Will I owe the buyer a refund even though I sold it in good faith following EA? If so do I then need to open a case against the seller back in Feb? it's all very messy!

Any advice would be greatly appreciated!