Again a reason why I gave up selling on eBay. Their attitude and PayPal’s (owned by eBay anyway) is always to support the buyer if they kick up a stink. Reversed payments and frozen accounts especially in PP when a buyer makes an accusation and then they get refunded, disappear and you have a fight on your hands to reverse the situation. That on top of large fees on the seller generally.
Will be interesting to see how things go when PayPal is split off from eBay. Particularly if this mean other forms of payment will be supported by eBay.
All that said, yes the ‘sample’ may be the reason for their belief it’s a fake. Similar with OEM versions of products and ‘seconds’ in clothing (seconds being official but imperfect in some small way). eBay listings should make it clear that this is what the item is else you may get this situation.
Some people are trying it on, some are just quite wary of fakes. They’ll look for small details like the labels etc which if different to what they expect if they’re well up on the stuff then they might think something’s fake.