I have discovered what seems to be an unreported but critical chunk corruption issue that is present at least in the newly released 1.20.30 Bedrock on Windows 10 and 11 (tested on both).

The image below shows what the corruption looks like. It looks like the chunks are mis-generated in 1.20.30 compared to 1.20.15, which is the second screenshot below. I'll provide some details on how to reproduce this bug and the world saves, as it can be consistently reproduced.

Reproduction steps:

1. Generate a new world in Minecraft 1.20.15. In this case, I used the seed 7671300184158697625
2. Because the issue seems to be visually easier to confirm in mountain biomes, I teleport to the coordinates show in the screenshots above. Now exit the game. 
3. Update to Minecraft 1.20.30 (this can be done using the unofficial Minecraft bedrock launcher to more easily reproduce, but the same issue also happens even without using the unofficial launcher). Load the world again and return to the same coordinates. The corruption shown in the screenshot above will appear, although not necessarily in the exact same spots.

From digging deeper my understanding of the problem is the following.

-Minecraft doesn't save all chunks that are visually present, just the ones you interact with or are closer to you, so not all chunks in the 1.20.15 screenshot without the issue have actually been fully generated and saved, even though visually all are present. These "missing" chunks can be confirmed by using a tool like unmined. 

-After updating to 1.20.30 and returning to the same spot, the chunks that were "missing" in 1.20.15 are now being generated in 1.20.30, which for some reason, generates these chunks differently. This is basically the bug. 

Some other additional information:

-This bug might have been around for a while, I tried the 1.19 to 1.20.15 transition and was also able to reproduce the issue. 

-Strangely enough, there seems to be a limited fix via the official chunker.app online tool. I had a world where these mountains (minus the "missing" chunks) were generated in 1.19, updating the game to 1.20.15 and returning to this region would actually manifest this problem. However, if before returning to this region (and triggering the generation of the "missing" chunks), one uses the chunker.app tool to convert the now 1.20.15 world, to the exact same version (by picking 1.20.10 in the chunker menu), if you return to this region, the "missing" chunks now generate properly. So the chunker conversion has done something to "fix" this problem. However, strangely enough, this does not work if converting to version 1.20.30 in chunker (so maybe the same bug manifest itself in chunker as well).

Finally, I have also attached the world download. The 1.20.15 file is the world save from the image without the problem while the 1.20.30 file is the world save from the image with the problem. 

I believe this issue is critical because 1.20.30 just got rolled out and everybody who generates new chunks on it will have this problem and corrupt their world.