Daily digests sometimes become one-message-per-digest

"Roger B.A. Klorese" <[email protected]> Wed, 31 Mar 2010 09:30:00 -0700

Newsgroups	gmane.mail.majordomo.majordomo2.devel
Message-ID	<[email protected]>

One of our lists has a digest definition that looks like this:

daily
times=5
maxsize=1024
maxage=1d
separate=0
type=text
sort=thread
index=numbered
desc=Daily Digest
subject=[$LIST] Daily digest - Volume $VOLUME Issue $ISSUE 
($MESSAGECOUNT messages)

...yet it seems on some days to decide to ship a digest for every single 
(much smaller than 1MB) message, and on others, to batch messages 
properly.  Any guidance on how to debug this?