There is an absolutely major bug with Bedrock world generation that causes biome-sized areas to generate in a corrupted state beyond 3,000,000 blocks or so. This effect might take a couple minutes of teleporting or flying around to find, or you might find several of them clustered together.

The split-screen screenshot shows Bedrock Edition alongside Java Edition, to show what the terrain should look like. This has also occurred on two separate machines.

To reproduce, use the world seed "Glacier" (without quotes), and teleport to the coordinates shown within some of these screenshots. To my knowledge, these chasms will show up every time. Given that 1.18 is about to release, I feel this is a pretty critical bug.