No matter what is attempted or where, on PC or on Xbox One (the two systems I have MCPE on) my Realms cannot download a copy of the world to edit texture packs applied, or download a previous backup of the world–although it can replace a current version of the world with a backup. This has been an ongoing problem I've had since December. Every time a download of the world is attempted it shows a progress bar for the file size until completed, and then says "FAILED"