Possible for fix for a race that has been plaguing me for years. If this

turns out to be the fix, I will be happy, and will need to clean up
things.

Turns out that it happened on one of the FEs, which are generally not
very active, and so the database logfile was on 60MB at the time, so I
could 1) load it into emacs, and 2) following along with that was
happening at the time. See commit 34eab295 for what I hope will make
this kind of chase easier next time.