I tried transferring one of my worlds and and it said it was 250mb. After it was finished converting it said it was only 190mb. I loaded the world and more than half it was erased and replaced with new terrain, effectively destroying my whole map. There are structures cut in half and missing completely

I had an issue the past few months where this world and all of its previous backups wouldn't load on the console edition before this update came out. Now it will load on the new edition but I have this issue now