Ebay don't get involved, as they cant verify items that are sent out or returned,so look at each case on a one to one basis if a case is escalated by a buyer,or a seller appeals a decision,if it goes in a buyers favour.
If a buyer opens a case of not as described in the listing,then a seller has to refund in full once they get the item back.
However,if the item returned is not in the same condition as sent, a seller can report a buyer for abusing the money back guarantee,if there is no evidence to show it was damaged in the post,See here,Report an issue with a buyer | eBay
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