Must be something in your MS install.
Updates for me don't require any manual "tricks", just quitting any open Office apps.
But, I also experience a slow deterioration of performance in Office apps, particularly PowerPoint (my main use) about once a year. Just slows down a little, with minor glitches.
Deleting the Office folder, then reinstalling from original installer, doing the latest update, helps bring back Office to its usual "glory".
I wouldn't take it personally - it's just typical Microsoft "treating" you with its own unequaled style.
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Try the uninstall/reinstall. Works for me! I don't even touch settings .plists or extensively "uninstall" from the various locations. Just delete the Office folder from Applications, and reinstall from original media. Only takes a few minutes (less than 10 minutes, IIRC, including updates.)