Simply, did not happen again.
So... question: why?
There are other sporadic and even consistent bootup errors which seem related
to timing. Certain initrd-releated items busy and cannot be removed, etc.
(Unfortunately, it goes by too quickly to write them down.)
<<Did not upgrade anything touching this, too my knowledge. Doing a
<<cat /dev/midi1 from the device connected to USB shows normal operation.
<<What gives?