Does it help speed it up and avoid errors if you also stop repagination and screen updates
Code:
Application.Options.Pagination = False
Application.ScreenUpdating = False
Don't forget to turn these back on at the end of the macro.
FWIW I have a strong dislike of Tracked Revisions and believe that tracking any more than about 100 of them in a single document is completely pointless. If you only track 'important' changes then tracked revisions have a real purpose (drawing attention to changes that NEED to be reviewed). If you track 7000 changes then no attention will be given to any more than the first page of changes. Word slows significantly with large numbers of tracked revisions and the likelihood of document corruption (or failing macros) increases significantly especially when multi-authoring in Sharepoint.