If we restore the course with the option "Delete the contents of this course and then restore" using an asynchronous restore task, below are the current processes.

1. Moodle will delete all the destination course's content.
2. Moodle will restore the backup file to the destination course.

The problem is the 1st step cannot be undone.

And if the 2nd step has some problem and cannot be completed, all the course's content of the destination is gone, and the destination course is completely empty.

We should do the backup/snapshot of the destination course and store it in a temporary place, right before the 1st step.

If the 2nd step has some problem, we can roll back the destination course to the original state by restoring the backup file that we already did.