The page numbers are in the footers, so maybe they need to be unlinked in some way. Somehow running page numbers right through all sections gets rid of the problem. But I think you are right, that there is something with section breaks. I have done this work before without these problems. But that is not how I wanted to run page numbers.
That worked! No more pages jumping around. Then I went back and instead ran page numbers right from the very first page, without changing any section breaks. I wanted the main body of the book to have its own page numbering, and that is normal. The problem began when I started to put in the front matter. I started this document with 25 sections (chapters), and each section ran page numbers from the beginning, but without a page number on the first page of a section. I got rid of all odd-even page breaks, substituting continuous breaks, and then blank pages before the break if needed.