CS25 Book Chapters in spread pdf sometimes works, sometimes doesn't
Using CS25 Indesign to produce a book exported to PDF. There are about 20 chapters. The same master is used for all pages: facing pages. Page numbering is set up consistently and correct: odd pages start on right, etc.
When exported to PDF as a spread. Some of the chapter breaks work just fine. But then, sometimes the last page of a chapter prints as a single page, and the first page of the next chapter prints as a single page. And then it reverts correctly to a spread. In the course of the 140 pages of the book, this odd behavior is repeated for about 10 of the 20 chapters. I've checked everything I can think of: in pages panel "allow pages to shuffle" is checked. Obviously I'm doing something inconsistently but I can't find out just what I'm doing to cause this sometimes OK and sometimes not OK performance. Any help would be greatly appreciated.
