That it says Section 3 means that it is the third section. There are two section breaks before it. Period.
There is no non-existent section break.
Any time you change the number of columns or margins in a document, you add at least one section break. They sometimes are at the very end of a line and all but invisible.
Here is my chapter on
Sections / Headers and Footers in Microsoft Word (Ribbon Versions).
It is helpful to set your status bar to show the section number.
It is often unnecessary to change sections to change headers and footers. See
StyleRef Field.
If you want, make a copy of your document and delete all but the problem pages so that it still is showing Section 3 where you do not expect. Attach that excerpt to a post here. You can delete most of the text if you want. The following article has information about clearing confidential or proprietary information from a sample document.
Why a sample file is important for troubleshooting. How to do it. In this forum, though, you can attach the file to your post, unlike in the Microsoft Community Forum.
If nothing else works, see
Toolkit for Advanced Management of Headers and Footers.
References that may help with your project: