Style Heading 4 in paragraph missing in Navigation Pane, Word 2013

In Word 2013, I changed text to heading 4 style at the beginning of paragraphs and it didn't appear in navigation, except for one phrase with no normal text after the heading text.

I have a long document (200+ pages) with Style Headings 1-3 for organization. I was manually adding a 4th heading at the beginning of some paragraphs and decided to switch to using Style, so they would appear in the Table of Contents (via Word Reference menu) later. I edited all those to Style Heading 4, and all but one were not added to the Navigation Pane. The one that was added had no paragraph (Style Normal) text after the Heading 4 text, while all the others did. I want all of the Style Heading 4 headings to appear in the Navigation Pane, and later in the Table of Contents when I add it. It appears that only paragraphs with Style Heading will add to the Navigation Pane, not text that is assigned to Style Heading in a Style Normal paragraph (even though the formatting changes to the set style).

To resolve this problem, I tried:

• Closing out of all Word documents and re-opening the file.
• Copying a segment of text and pasting it into a new Word file. This did not fix the problem, though all the other heading styles copied correctly.
• Checking the Styles Pane for incorrect data. There were no differences between the heading that appeared in the Navigation Panes and those that didn't.
• Adding a paragraph space between the Heading 4 text and the Normal text. This did not add it to the Navigation Pane. I use Word with "Show Formatting" enabled, so I noticed the paragraph marker was still black after the Heading 4 text. I selected the line and changed the whole thing to Heading 4, the paragraph marker turned blue, and the Heading 4 text appeared in the Navigation Pane. Then I tried deleting the space to get my paragraph back where I want it, and it changed the whole paragraph from Normal to Heading 4. It then locked, and wouldn't let me change the paragraph back to normal. I had to undo to get it back to the Styles I want, removing it from the Navigation Pane.

Below is a simplified Style text layout. Heading 4a doesn't show in the Navigation Pane, but Heading 4b does. All the other Style Heading text appears in the Navigation Pane, and doesn't have additional styles in the paragraph, like Heading 4a does.

X. Heading 1

normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal

A. Heading 2

normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal

1. Heading 3

normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal

a. Heading 4a. normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal normal

b. Heading 4b.

normal normal normal normal normal normal normal normal normal normal normal normal normal

Is this a bug? If yes, is there a workaround that will let me keep normal paragraphs with headings that show in the navigation pane? If not, what am I doing wrong?

Thank you!