I have right now the same problem like the topic creater. I have done the steps like the solution of Mr. Ken, but in the end I have a problem to get the get the files from the symbolic link path. It ends like in this topic: https://moodle.org/mod/forum/discuss.php?d=311867
Our moodle platform is running on version 3.1, maybe it's there the problem with the access via symbolic links?
Is there another way to access to backups which are located in other repositories?