A big thanks to Jeff for talking with me offline and giving a bunch of suggestions, and for Tim for noticing from the output of the 'sasadmin expander_map' command that I've got some mis-wiring in my setup. Which is strange because we haven't re-wired this system in ages, not since we moved it across country three or four years ago. And the warnings havent come back again either. So far. So I think I'll just table this for now and maybe think about re-wiring it all when I'm next on site and have the downtime.
Thanks again! John