FOLLOW THE MONEY
The error code associated with the problem was always the same: 2003332927. Today, I googled it and this site showed 4 results for the error code. The first three were audio related (getting closer). The last was one was a mediaIO error! Hot on the trail!

I went thru every folder and subfolder in the main Library. I thought I had removed all things Logitech but buried in a subfolder was a tiny little file in Library/CoreMediaIO/Plugins/DAL/LogiCapture.plugin

The culprit!
Deleted. Restarted. Voila! Fixed.
It was NOT a MOTU problem. It was a Logitech problem. The unicorn lives on. Damn the harpies; full speed ahead!
