The Bug:

Near the top of the nether at y level 121, cave carvers always get cut off, resulting in caves and ravines having flat ceilings.

Here is an example:

Seed: 1692907036
Coordinates: /execute in minecraft:the_nether run tp @s -207.04 114.23 412.72 105.38 -46.64

Steps to Reproduce:

1. Generate a world with the seed provided above and teleport to the given coordinates.
2. Look closely at the ceiling of the cave/ravine.
3. Take note as to whether or not caves and ravines near the nether roof have flat ceilings.

Observed Behavior:

Caves and ravines near the nether roof have flat ceilings.

Expected Behavior:

Caves and ravines near the nether roof would not have flat ceilings.