Thanks for the various suggestions, but at the moment I'm not into 'correcting' something that I don't understand and which might not even need 'correcting' — especially since it happens only every so often and doesn't seem to have other than momentary import to the machine(s) and backup process.
I just want to know what's going on and whether or not it's a real problem.
All I can gather is that for some file save events the backup function can't determine a path and stops trying to but which in turn doesn't cause the backup process to abort or not complete.
