On our site we purchased the Karma theme because it worked with Woo Commerce. Everything was working great until everything after "Your Order" disappeared. We looked at the network tab on Chrome dev tools and found that when admin-ajax failed to load it would just zap that section.
We tried to fix it a few ways and eventually just reinstalled WordPress and it was fine. Until it went down again that night. So we reinstalled wordpress again. And it went down again the next night.
We thought it might be a cron job so we ran each and tested individually and haven't found it to be one of the cron jobs.
We have Paid Membership Pro, Woo Commerece, Woo Tickets, and the Karma theme as the base of just about everything on our site.
What could be causing the cart to die? We really can't just reinstall wordpress every few hours. :)
ldsamcap.org/checkout is where the problem occurs. Even with the checkout options working ajax-admin take 3 seconds to load. Seems long.