Kindle "sees" only first item in the TOC

[gjbalzano]

Some of my ebooks show the following display problem when I try to read them on a Kindle: Although the nominal TOC contains all of the chapters, properly named and sequenced, when I tap the top of the Kindle screen in to see "where" the current page is in the book, what displays at the bottom of the screen is not the actual chapter where the page is located, but rather the FIRST chapter in the TOC, i.e. all pages in all chapters are seen as "belonging" to the first chapter.

I can't seem to track down the source of this problem, or why it occurs only in some books and not others. There appears to be nothing unusual about the toc.ncx file for the offending books; some of them say (e.g.) the "dtb:depth" is 1, some say it is 2 (changing the value has no effect on the problem). Can anyone tell me why problem might be happening for (a small percentage of) my ebooks?