Word 2016 - Keeps Changing Markup Settings

Hi Experts,

Periodically I have a problem with Word when I open a document.  It shows markup of the whole Table Of Contents.  The Markup Settings when the document opens are as follows:
- All Markup.
- Show Markup: Comment, Insertions and Deletions, Formatting options are checked.

If I change the settings to the following the markup disappears which is what I want.
- No Markup.
- Show Markup: Comment, Insertions and Deletions, Formatting options are un-checked.

I then save / close the document and when I open it the next time the Markup Settings are changed back to the following as though I hadn't changed them and the Table Of Contents shows the markup again.:
- All Markup.
- Show Markup: Comment, Insertions and Deletions, Formatting options are checked.

How can I get the new setting to 'stick' so that the markup doesn't show?

Thanks,
Bob C.