Previous version of Writer would create a bookmark from each header, and then export them nicely to PDF. In 4.3.0.4 the bookmarks don't show up either in the bookmarks page of Writer or in the PDF. Help is not helpful.
I meant headings, not headers. Manual insertion of bookmarks also seems not to be working. The only bookmark that shows up in Navigator is an incorrect one from an earlier version of the document, despite several attempts to add a new bookmark.
I found the problem. Somehow a "go back" code has appeared in the bookmarks list. Once I deleted that everything worked. No idea how it got there or how to generate one.