A family of Microsoft word processing software products for creating web, email, and print documents.
It isn't the Section Breaks that are creating the problem. The Document Map has no awareness of Section Breaks, its content is based strictly on paragraph formatting using Heading Styles or Styles that include the Outline Level 1-9 attribute.
Without seeing the document my first guess is that the return key has been used to manufacture 'blank space' in the document. If you'll display the non-printing characters (¶) you'll see that there is a vertical series of those symbols in the document, i.e.;
¶
¶
¶
¶
¶
¶
Those symbols represent empty paragraphs that correspond to the gaps in the Document Map Pane. Each one of those paragraphs carries the Style formatting that causes it to be recognized as a Heading. If you delete those meaningless empty paragraphs the gaps in the Document Map will be removed as well.
If there is a valid reason to have vertical space in the document there are more appropriate ways to do it rather than beating on the return key :-)