i faced same issue lately, after optimized and filtred some website as white list the AP goes down, i just made another Run (Retest with no white list) and increased the bid. i discoved some new website ID that wasn't appear before with old bid, after few hours the AP goes to normal value, the campaign is running for 2 days now with nice ROI.
So from my last experience i can tell you that your white list is containing ID's that give low traffic quality as my manager said.