I am back to troubleshooting, yet again, the problem of Moodle backups taking forever and a day. An actual day, for very small courses.
A second problem occurring with the automated backups is that the old backups are not being purged so the file system is filling up with them rather than purging/pruning them. I am solving the problem at present by a weekly manual clean up.
I could simply pour over the forums for an answer, which has not produced results. I could look at tables/records in the actual database for anomalies and that strikes me as time consuming. Or I could wait until the semester break in two weeks and backup and export each class and all the information and create a brand new instance of Moodle and restore the classes into that and see if that leaves the cruft and problems behind.
I am going with that alternative in the interests of cleaning up any other problems I am not yet aware of that affect other areas including performance.
Will post my results.