I'm glad you were able to get it fixed.

Word 2013 is a pain, but I am only aware of one bug, and this is not it.

Sections have been causing problems with page numbering forever because you can have multiple sections on a page and any of them can tell page numbering to restart, even though the section that does this does not actually show any page numbers itself. Chances are that it was Section 4, then, that reset the page number and when you were in section 4, you were seeing the Section 3 page numbering in the footer.

I believe that the headers and footers displayed on a page are determined by settings in the secgtion that begins the page.