PDF bookmarks under wrong chapter

This is a nagging issue that's been affecting myself and the other writers in my company, and nobody is sure how to go about tracking down the problem. After finishing work on a FrameMaker book and saving to PDF, the bookmarks in the PDF are all shifted into the previous chapter. The contents and TOC are not affected, only the bookmark hierarchy in the PDF. As far as I know, all of us are running Windows XP SP3 and Frame Maker 10.

Here's a basic example of the problem. Each chapter is its own document.

What it should be:

Chapter 1

-Ch1 Heading 1

-Ch1 Heading 2

Chapter 2

-Ch2 Heading 1

-Ch2 Heading 2

Chapter 3

-Ch3 Heading 1

-Ch3 Heading 2

Chapter 4

-Ch4 Heading 1

-Ch4 Heading 2

What I get:

Ch1 Heading 1*

Ch1 Heading 2*

Chapter 1

-Ch2 Heading 1

-Ch2 Heading 2

Chapter 2

-Ch3 Heading 1

-Ch3 Heading 2

Chapter 3

-Ch4 Heading 1

-Ch4 Heading 2

Chapter 4

*Notice that these headings are now promoted to the same level as the chapters.

If it can't be fixed, it's not a big deal since we can just correct the bookmark order in Acrobat. It's just a matter of remembering to do that every single time.