BIND 9.2.2: zone transfer lower-cases some data

Platform: BIND 9.2.2 on Solaris 8

Zone file is an in-addr zone, has mixed-case values as targets
of the PTR records. e.g.

2.1.168.192.in-addr.arpa 12H IN PTR foo.Example.ORG.

When you pull the zone file, the first 900-1000 PTR records
come across with the PTR record targets all lower-cased
("foo.example.org"). The remainder come across correctly,
with their original case preserved.

The problem appears to be at the server side, not the client.
You can reproduce it by simply pulling with the client of your choice.

It's more than a cosmetic issue.
(An example of an application that cares is Solaris NFS export
lists that refer to NIS 'netgroups'. It unfortunately does
hostname comparison without ignoring case.)