One thing to remember when dealing with high traffic websites is that the webserver can actually be an array of webservers. One such website, I'm told, has more than 200 webservers which balance traffic among them, and (when new content is being rolled out) they don't necessarily all have the same version of web content or services.

The behavior you describe has the sound of a webserver with locally cached data, which can be expected to be cleared out or expire over time, or differ in the case of an alternate webserver.

It might be worth your while to see if there are any services deployed which would give you cleaner, more reliable access to the data you need.