Error cannot save term in required managed metadata column

My SharePoint document libraries that have required managed metadata columns without a default term cannot save metadata if a user follows these steps:

1. Create a new Word or PowerPoint document and start editing the content or name
2. Close the document tab
3. Go to the document library view to resolve the "Required info" prompt
4. Use any properties controls -- sidebar, in app, edit in grid view -- to try to change the "Type of Document" column I created to select a term.
5. The term will show briefly until user hits "enter" to escape and save the selected term
6. Properties window refreshes, selected term disappears and messages say "missing required info"

No issues with Excel.

No issue if there is a default term, but I don't want that.

I cracked open properties in Windows to see that the column on these particular documents is not getting saved as "Type_x200_of..." but "Type of" ...