I feel your pain.
Lots and lots of backups - including off-line backups. A Master Document has the ability to corrupt parts of the document that are not even open!

You might want to add the term Master Document to your thread heading. Also replace "outline" with "Master Document" in your tags. Because of the bugs in this "feature" few experienced Word users have much experience using it. Generally one "experience" is enough.

You might want to get a copy of Microsoft Word 2010 Bible and show Herb Tyson's remark to your superiors. It is colorful and gets the point across. I don't know of anyone who ever tried using Master Documents that was working on something he/she could afford to lose.