Hi Mathieu,
We have the MoodleCloud for school mini pack with 100 users. In the courses we want to restore, 46 users are present at most.
The first restore was ok (and it has populated the user database) but after that it failed for each other courses. And when we have deleted the restored course we could not restore it again.
I suppose that each course restoration attempts to add again participants as users.
When I restore courses without user data it is ok but I think I have a problem with the user database anyway. At least one account cannot be deleted ...