The borders are drawn on every page, even those that do not contain header/footer content — like the title page, empty pages, index, etc.
Since the content is empty, the region height is different from the populated headers/footers, so the border lines appear in different places than they do on pages with real headers/footers.
Not sure how easy this is to change, but would be elegant if borders were only drawn on pages that actually contain header/footer content.
When borders are applied to running headers/footers:
The borders are drawn on every page, even those that do not contain header/footer content — like the title page, empty pages, index, etc.
Since the content is empty, the region height is different from the populated headers/footers, so the border lines appear in different places than they do on pages with real headers/footers.
Not sure how easy this is to change, but would be elegant if borders were only drawn on pages that actually contain header/footer content.