On reflection I think the cause may have been all the back and forth with partitioning and then undoing partitions. With the backups and my intended "32 bit drive" on separate drives…
It may have been all the back and forth with partitioning
etc. but sometimes the Launch Services Database gets messed up without any apparent "help" at all. However, like many things that can go "bump" in the system, as OS X/macOS has matured it happens less and less often — but it still happens, albeit rarely.
I figured it was goofy as hell to leave the main drive partitioned so I restored it to one partition.
👠IMHO that was a good decision. Two or more APFS volumes on the same drive gets around the most egregious problems with partitioning and is acceptable, but partitioning is too restrictive and too inflexible.
BY-THE-WAY, I have two external HDs that I use for archival data storage that are formatted APFS with multiple volumes (so I can have a different encryption password for each volume) and those are working very well. APFS may not be the optimal format for rotating rust but any performance differences are unnoticeable.
