FWIW one of the old replies by ysth
in one of the threads listed in one of the links listed by chacham talked about caching being the source.
Lost the link and can't find it anymore. HTH!
found it Re: DBI and PP not behaving... resp. Re: Discrepancies in the number of replies for correct context (should probably be reparented)
(tye)Re: Node reply count bug?