Not totally certain on this, but here are some additional factors.
recent Windows updates
Dell Disk Protection (DDPE)in use
Thus far, the following has been working:
Outlook
Rename OST file and allow to rebuild
Word, 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