Converted Xbox One World To Better Together Update Version World Loads New Chunks Over Previous Chunks

(Issue reported for a friend)
Images are taken from PC Windows 10 playing with a Xbone Account

When converting a world over from xbox one to the better together version, upon loading the world, many new chunks are loaded over old ones. We have lost many hours of work on this world. The new chunks are mainly placed around where the world spawn was set. The world is a converted world from Xbox 360, which was put on Xbox One until we tried putting it on Better Together.

Please, is there any way to get around this? I've tried looking (maybe not hard enough) and couldn't find anybody else with this issue.