deja-dup-monitor scheduled backups broken

[Jack Howarth <howarth mailing lists gmail com>]

     I have been using deja-dup 34.2-0ubuntu1.1 on Ubuntu Xenial 16.04 for a couple of years now with a extra hard drive selected as the destination for the backups of my user account from a SSD. At some point, the auto-mounting of the secondary hard drive got disturbed and deja-dup failed to perform a backup due to the backup disk not being available. I changed the mounting of the secondary hard drive to a hard mount in fstab instead of automounting. However the deja-dup-monitor still fails to execute the weekly backups despite Backups showing that the weekly backup is scheduled. Since switching to a fstab mount instead of automounting, the backup drive not available dialogs have disappeared and manually executed backups from the Backups app succeed. 

     Any idea why this the schedule backups are silently failing to be done by deja-dup-monitor? Using...

    gsettings list-recursively org.gnome.DejaDup

I have the expected settings...

org.gnome.DejaDup last-restore ''
org.gnome.DejaDup periodic true
org.gnome.DejaDup full-backup-period 90
org.gnome.DejaDup backend 'file'
org.gnome.DejaDup last-run '2019-06-18T12:03:32.004990Z'
org.gnome.DejaDup nag-check '2019-05-14T02:44:45.897034Z'
org.gnome.DejaDup prompt-check 'disabled'
org.gnome.DejaDup root-prompt true
org.gnome.DejaDup include-list ['$HOME']
org.gnome.DejaDup exclude-list ['$TRASH', '$DOWNLOAD', '/home/howarthjw/Dropbox', '/home/howarthjw/googledrive', '/home/howarthjw/VirtualBox VMs', '/home/howarthjw/arionax_googledrive']
org.gnome.DejaDup last-backup '2019-06-18T12:03:32.004990Z'
org.gnome.DejaDup periodic-period 7
org.gnome.DejaDup delete-after 0
org.gnome.DejaDup.S3 id ''
org.gnome.DejaDup.S3 bucket ''
org.gnome.DejaDup.S3 folder 'ArionAnalytics'
org.gnome.DejaDup.OpenStack authurl ''
org.gnome.DejaDup.OpenStack tenant ''
org.gnome.DejaDup.OpenStack username ''
org.gnome.DejaDup.OpenStack container 'ArionAnalytics'
org.gnome.DejaDup.GCS id ''
org.gnome.DejaDup.GCS bucket ''
org.gnome.DejaDup.GCS folder 'ArionAnalytics'
org.gnome.DejaDup.GDrive email ''
org.gnome.DejaDup.GDrive folder '/deja-dup/ArionAnalytics'
org.gnome.DejaDup.Rackspace username ''
org.gnome.DejaDup.Rackspace container 'ArionAnalytics'
org.gnome.DejaDup.File path 'file:///mnt/f99d800d-0553-4129-884f-07fbe107e35a'
org.gnome.DejaDup.File short-name 'ExtraDrive1'
org.gnome.DejaDup.File uuid 'f99d800d-0553-4129-884f-07fbe107e35a'
org.gnome.DejaDup.File icon '. GThemedIcon drive-harddisk drive'
org.gnome.DejaDup.File relpath b''
org.gnome.DejaDup.File name 'ST4000DM005-2DP166: ExtraDrive1'
org.gnome.DejaDup.File type 'volume'

Is there some other location which holds configuration settings that I should be checking to try to figure out why the scheduled backups have stopped since deja-dup ran into the backup volume being unavailable when it was still on automounting?