I just posted this very question Friday, but mine were changing from "New
Page" section breaks to "Continuous." I then discovered that if I go into
the section following the actual break mark, and then pull up "Page Setup"
from the "File" menu, and look under the "Layout" tab, at the top, there is
"Section." Make sure that is changed to whichever type of section break you
want. I think you will find that it's "Continuous" there, and that is why it
keeps changing it. Hope this helps. It fixed my problem.