One thing you never mentioned - what version of slapd are you running?
2.3.32
I still don't see any particular failures occurring here. If your client isn't having any problems I wouldn't waste any more time worrying about it.
It's entirely possible that I'm chasing a red herring. My primary goal in posting here was to find out what, exactly, the deferral messages indicated and, from that, whether or not they could be responsible for the problems I'm seeing.
Thanks to the very clear, helpful responses from you, Pierangelo, Hallvard, and others I'm fairly confident I'll be able to rule the deferrals either in or out as relevant to my problem with a few more troubleshooting steps.
Thanks!
-Ben