I get items duplicated on eBay once in a while when sent from M2Epro on my magento site. Often I get products duplicated on eBay. So there is one product on my site but somehow two get sent to eBay. Sometimes I can find them when I look in the 3rd Party Listings section of M2E and I end them, but other times they appear in ebay but there is no record of them on M2E.