Never allowed means what? Never turned on?
Do you have more than one admin level user?
Has autobackups been turned on without your knowlege?
Other than teachers themselves doing backups, in Moodle code
only the cli script in moodlecode/admin/cli/autobackup.php
provides that function. And to access/run those one has to be logged on and execute via
command line. Unless you've hacked code.
Obvioiusly, factors ... your script/code. You've not shared any info
on that. Have never heard anyone say system doing backups all by itself.
Did you look at reports for automated backups in Moodle Admin? Although nothing would be there on something you've programmed me thinks.
This eror "cannot_finish_ui_if_not_setting_ui" means something interputing a backup process. Seen that in a situation where admin was attempting to restore the same course multiple times by using same browser with 3 active tabs attempt to perfom a restore of the same backup file. That system (a 3.5.3+) was loosing track of stages etc. Errors always showed staging had reached 700.
Now what about your scripts? How are they run? In some sort of timed process? What happens when one fails ... does it log which backup failed and schedule that course fora later time?
Am not capable of Vulcan Mind Meld! :| Encourage you revisit your scripts/system/logs, etc.
'spirit of sharing', Ken