It is not uncommon for documents to show changes due to various reasons. The following list outlines potential steps to take to diagnose these changes.

1. Review any recent changes made to the document.
2. Check the preferences of applications used to work on documents (e.g. Word, Powerpoint).
3. Check for any macros set up that may have been disabling track changes.
4. Check any third-party plugins or apps that may have been installed.
5. Check for any system-wide keyboard shortcuts that may have been set up.