Chapter numbering resets unexpectedly

["Adam Preble" <adam@stradis.com>]

Hi all,

The chapter numbers in my docbook HTML output are resetting in unusual
places.  The structure of my document is:

    book
      part
        chapter
        chapter
        ...
      ...

Most settings are at their default, including chapter.autolabel (on). 
After processing, the part numbers are correct, but the chapter numbers
are: 1, 1, 2, 1, 2, 1, 2, ..., 8,  9.  All 13 chapters are in the same
part, and they are continuous - just a part with a title, intro paras, and
chapters.  Any ideas about why they would reset like this?

I'm using docbook-xsl-1.64.1 and xsltproc.  (problem also happened when
using 1.62)  I've tried removing my customization layer - no change to the
numbering. 

Thanks for any help,

Adam