The closest thing in my experience, is when Word is trying to keep track of a document whose sections have not been properly formatted. For instance, footers having been created for landscape pages that are too wide for the portrait pages, but the footer's "Same as previous page" is still on. Word keeps trying to repaginate, which can gum up the works in a similar way, if not exactly the same.

It is possible that a look in draft (normal) view will reveal something you are not seeing in page layout view.