Table of Contents Macro: Position of Heading 6 Changes Based on Heading Size Following it

When using a Heading 6 after using the Table of Contents Macro, the position moves based on the next Heading. Reported for version 5.4.4 but I replicated in 5.4.4 and 5.5.4.

Reproduction steps:

1. Create a new page
2. Insert Table of Contents macro
3. Type a line, make it Heading 1
4. Type a second line, make it Heading 6
5. Type a third line, make it Heading 1 and save
6. Edit the document, make the third line Heading 2 and save
7. Continue changing the heading type for the third line

Expected behavior

The position of the second line should stay the same, only the position of the third line should change

Actual behavior

The position of the second line moves based on the heading type used for the third line.