I'm unable to change the footer from one section to the next. The first
section is portrait and the second is landscape.

The problem appears to be that the new-page section break that I have
inserted changes to a continuous section break. I have tried using various
settings in the Page Setup: Section Start (continous, new page, odd page),
but these don't make any difference.

When I insert a header or footer in the second section, it appears in the
first one. "Same as previous" is unchecked throughout