Hi,
Moodle has not an option to cancel scheduled backups, in my case, I had to delete the backup's database register to cancel it.
The table where are the backup registers is called mdl_backup_controllers.
Then you have to delete it (DELETE * FROM mdl_backup_controllers WHERE backupid = {backup id to cancel}).
To know backup's id you have to inspect the progress bar HTML element.
Moodle has not an option to cancel scheduled backups, in my case, I had to delete the backup's database register to cancel it.
The table where are the backup registers is called mdl_backup_controllers.
Then you have to delete it (DELETE * FROM mdl_backup_controllers WHERE backupid = {backup id to cancel}).
To know backup's id you have to inspect the progress bar HTML element.