Could this guy be a fraud?

Hello guys, I s3ll digital items on eBay, and some user orders my item right, and than another user orders. I have a quick look at his reviews and it looks like he has the same reviews as the other user and the user ids are very similar. He has about 4+ accounts purchasing my items and ive been delivering them. The User ids are from different locations around the world and are all created from 2015 October+, all of them have positive reviews, this user also buy from others in the same niche as me.

Too summarize, over 4 accounts that could possibly own to one owner are purchasing my digital items, he denies that they are his accounts. If it is fraud, What should i do?