Summary:

The pass from the mine was generated too low and reached the bedrock (without breaking only two layers). It seems that the bedrock should not be on the surface and the passage seems to have destroyed a bit of the bedrock.

This is not a single seed problem. Entire corridors can also be generated, destroying the bedrock.

Seed and coordinates (1.17.30):

Seed 2074260135
Coordinates -1306 -51 1449

Seed and coordinates (1.17.40):

Seed: 47664
Coords: 5900 -61 5165

Steps to reproduce:

1. Create a world with the specified seed ("Caves and Cliffs" enabled).
2. Visit the coordinates indicated on the screen.

Observed results:

The mines pass was generated too low, causing the bedrock to stand on the surface and partially removed to generate the shaft pass.

Expected results:

The generation should not have a bedrock on the surface, and the mines must not destroy the bedrock.

Image: