UPDATE: Just found solution in this thread. Worked a charm!
46.7 Gb recovered. This is slightly more than might be deduced from above but is what Finder is reporting before and after.
So it was indeed a Snapshot problem, but not one that could be resolved by simply deleting snapshots in Snapshot manager.
I just used it on another VM and recovered 10Gb that I had not noticed was missing.
Seems like this ought to be a maintenance activity form time to time.
Last edited: Apr 24, 2016