For setting the style for headers and footers, there is for each a check box "Same content on first page" in each of the tabs for "Header" and "Footer".

Each of those two check boxes may be independently set

However, on the document if I enter a unique header for the first page (having unchecked the box on the header tab), and then go to the footer style and check the box (so the footer will repeat on the first and following pages),

The header i wrote disappears, and behaves like it is also repeated from first and following pages.

Oddly, if I go back and .re.-set the header checkbox, the content reappears.