Ok - so have made progress - looking at the 3 Indicators for that source and then at their 5 Breakdowns I see that one has "blank" Breakdown Name! Quite how that happened I don't know - I shall remove it from the Indicator(s *3) and expect all to be well. May account for the message not including a name
I can also report that this message is generated when you have forgotten to set a "mapping" between a newly created Breakdown and the field on the relevant record.
Not exactly "disabled" more like "not enabled" or "not complete"
