We have the same issue but it is not limited to track changes mode and everyone on our team works locally. We have sent screen shots of the same exact document which shows with different format (i.e. some lack spacing between paragraphs while others have them). We can have three different Word users looking at the same document - only one sees formatting that looks correct while others have huge blank pages, extra spaces or no spaces.
Are all users running Word under the same operating system?
Is each affected document set up consistently with styles?