Recently I was trying to move Minecraft bedrock world's from a old tablet to my PC, I just droped the world files into the game files. When these world's loaded I noticed that mutiple chunks of the world were gone. Any blocks in these chunks including naturally generated ones were gone. Today I checked my phone to a world I had ported to it. It had the same problem loading previously generated chunks. I have entered a screenshot of the problem and I hope it gets fixed.