Retracted bids

[missmarple63]

I have found proof that a buyer is making constant retractions to bids on auctions, and then re-bidding on the same item with one seller. I have already counted at least 6 different auctions from same seller, and I'm not finished auditing! The bid retractions are not a decimal point change, or because of sudden description change. In several instances, the buyer outbid me, then changed his/her bid lower. It was a clear example of manipulation to see what my highest bid was. What do you think that I should do? The seller doesn't seem to want to take responsibility for the buyer's actions by canceling the bids even though I brought the matter to their attention. Any suggestions? Should I just assume that these auctions are tainted?

Thank you.