I have tried to use my iPad to download my world into my empty worlds list. It proceeds slightly longer into the download but shortly after reaching 1.3gb bounces back to 1 gb then fails.
My realm world is fully playable on both devices Xbox and iPad with no glitches or crashes but can not be backed up or downloaded.
There maybe an issue with some older texture packs and VV causing this issue. I removed my only texture pack which was the minecraft default textures and it finally downloaded.