On your advice, I've done both. When I ran Disk Utility from the MacHDD it ran though 20 snapshots and continuously had the message "error:directory valence check:directory oid 0x130063: nchildren (2) does not match drec count (0)
I ran Spotlight Index and it seemed to be very fast, so I also rebuilt the directory with OnyX...and it seemed very fast (almost instantaneous)
Then I booted in Recovery and ran DU in repair mode. The previous message was replaced with: fsck_apfs-n-l-x/dev/rdisk2s1 When done, DU said everything was fine.
I rebooted into my macHDD and reran DU. The previous message had disappeared and it confirmed everything was fine.
However, when I tried to index Spotlight in the prescribed fashion, it cautioned: "Are you sure you want to prevent Spotlight from searching in macHDD. If you exclude this location from Spotlight searches, the search feature won't work in some applications."
So, I went back to OnyX and it did it, again very fast.
So, all in all, I guess things have worked out. Thanks.
