BIND not loading into memory on first transfer

[Frank Even]

The subject is about the only way I can think to describe a situation
we've run into recently.  First here is the system:

[root at dns]# cat /etc/redhat-release
CentOS release 6.6 (Final)
[root at dns]# rpm -q bind
bind-9.8.2-0.30.rc1.el6_6.2.x86_64

So, we got bit by a chroot permissions issue (unsure exactly how it
got introduced), where the chroot was owned by root, but had named as
the group owner.  Perms were 750 on the dir (rwxr-x---)

Zone files were in place for the necessary domains, but were outdated
(assuming one of our updates broke something somewhere, they were all
on average 3 months old).

We updated some of the boxes, and on restart, named started.

It initially started loading the 3 month old zone (one frequently
updated I might add).  The boxes then did a zone transfer from the
master.  Failing to be able to write the tmp file to the working
directory, it moved on.

Here is where the issue is.  I've generally found if BIND fails to
write the zone, it generally loads it into memory (masking the fact
that there is an issue here for an extended period of time).  In this
particular instance, the masters ended up under maintenance shortly
after these boxes rebooted, so they were unable to transfer the zone
from them for another 2 hours.  These boxes were serving stale data
after boot despite being able to accomplish one zone transfer after
boot.  It seems that failing the first zone transfer did NOT load the
zone into memory (but subsequent zone transfers while still failing to
write the tmp file DID load the zone into memory).

I guess the question really is, is this expected behavior or a bug?

Thanks,
Frank