by Ken Task.
Am looking at/using a Moodle 3.7.3+ (Build: 20191115)
Hmmm ... 'locked in the backup' ... you are working with a backup from your site and not a backup acquired elsewhere?
Wonder if there is a setting in the backup file itself. Only way to find that out is to un-compress the backup file then inspect the .xml files to see if there is a locked setting. I'll take a peak at that and get back.
How was your Moodle installed in the first place ... by some one button click installer like 'Softaculous' or other provided by hosting company?
'SoS', Ken