At the start of November I sold a second hand camera on eBay, in full working order to the best of my knowledge.
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I would prefer not to refund or accept the return as I don't believe I sent a broken item (he could have damaged it in the last month and a half), and he really ought to have checked it when he received it.
True, though are those statements above because you also didn't check it before sending it?
I think you're covered though, obvs there are some limits here and you can't just have some unlimited liability whereby at any point in time a chargeback can be made, ebay does set this to 30 days under the money back guarantee for "not as described" items (which includes broken items).
I guess the main question then is how sure are you really that it was working/what is the buyer complaining about specifically? If it was a Christmas present then that's quite a plausible reason for them not finding out until now and if they did want to scam you then surely they'd have done so in the 30 day period. I wouldn't personally want to have sent someone a faulty camera and you accepting the return just puts you in the same position you were before.