Yes, I might try the Repair, Richard. I'm not in a hurry to do a full rebuild as the system is fine in all other respects. Though having said that, this installation, with updates and lots of experimentation, has been going for a year now. A refreshing rebuild, rather than a renovation, to use a construction-worker's terms, might be appropriate.
Also, trying to diagnose and fix the problem is educational, so while I have spent time on it, I've learned stuff on the way. Just have to remember it now
Thanks again
AA