Not totally certain on this, but here are some additional factors.
recent Windows updates Dell Disk Protection (DDPE)in useThus far, the following has been working:
Outlook
Rename OST file and allow to rebuildWord, Excel, etc
Sign out of the O365 account Delete all O365 / Office saved credentials Delete all folders that end with CACHE in the %localappdata%\Microsoft\Office\16.0\ Delete Word Normal.dotm Delete the Auto Correct file (no aways) at C:\Users\Name\AppData\Roaming\Microsoft\Office - generally just deleted them all Sign into Office using Word or Excel