Automatic numbering in Word is a whole world unto itself.
Your styles need to be set up in a particular manner described at How to create numbered headings or outline numbering in Word 2007 and Word 2010.

Changing the numbering on one of your styles without following this procedure will lead to what is known by the technical term "spaghetti numbering." Not what you want. While numbering done that way may work in a document until it is edited, using it in another can cause problems.

Suggestion. Set your numbering up fresh in a new template (not document). Create new documents or templates based on that template. Copy your content from your old documents into the new ones using the styles and formatting in the destination (new) document.