User blog comment:DaNASCAT/Technical Update: June 5, 2017/@comment-32638135-20170605194548/@comment-5973717-20170606023952

WAM breaks so often because Wikia is supporting tens of thousands of wikis at any given moment, calculating the total activity for a particular wiki is a somewhat intensive on its own, and scaling that up to such a degree is even harder.

In summary, WAM breaks so often because it's really hard to make and maintain a tool that does what WAM has to do.