We were experiencing a lot of ad collapses across the site and believe it may be related to AAX. so we have paused AAX while we look into the issue further.
Update: The ad collapses were indeed due to AAX. AAX was updating logic on their end to be able to detect mobile adblock users, and as a result were collapsing ‘top’ and ‘left_top’ ad slots all over our site. The issue was live for ~5-8 hours. We did notice viewability for those units dropping to below 50% viewabile at that time as a result since the creatives were serving to the slots properly, but the AAX script caused the slots to collapse after ad load.