When syncing old worlds, some chunks are randomly re-generated, destroying builds and chests.

When I synced up and transferred my Xbox One Edition world onto the new BETA game, some of my chunks regenerated, cutting my castle in half and destroying my valuables chest (including all of my iron and diamonds). I'm sure this is just a bug for the beta so I'm not too worried, but I'm just concerned because it only happened to a few chunks in my world.