Cox clamping VPN traffic?

I've got a local peer with Cox for VPN users to co-lo. A VPN connection that otherwise shows no issues just had their file transfer rate during a large file transfer over the VPN go from 10Mbps to 43kbps, and stay there. This isn't transit, it's local peering. The local Cox guys don't see anything wrong. Other users can access the same server over their VPN with no problems, and the end user has no issues transferring large files from other sites. Looks to me like the P2P bandwidth clamping "solution" gone bad. Anyone have any insights into what Cox are up to? P.S. The Cox customer using the VPN has a Cox Business Services link, not a home cable modem.