On approximately June 6th/7th, my Winning Bid Revenue and EPC took a major hit. My EPC has been moving downward since and is now at about 50% of where it was on June 5th.

I believe that eBay rolled out some new EPN code at this time, probably related to this blog post:
Upcoming Changes to the Finding API for Affiliates | eBay Partner Network Blog

I am using the Finding API, so I would not be surprised if the new link structure, which I am using, is the cause.

Has anyone else experienced a similar drop over the same time period?