Reproduction steps:
1. Open the attached project "ReproProj"
2. Open the “/Assets/Scenes/SampleScene.unity” Scene
3. Enter the Play Mode
4. Observe the Game view

Expected result: The CharacterController is stopped by the cubes
Actual result: The CharacterController moves towards the cube and falls through the ground

Reproducible with: 6000.0.65f1, 6000.3.4f1, 6000.4.0b4, 6000.5.0a4

Reproducible on:
Play Mode
Windows Standalone Player

Testing environment: Windows 10 Enterprise 21H2
Not reproducible on: No other environment tested

Notes:
- If you disable a single Cube, the CharacterController will stop falling through the ground
- Does not reproduce when using a Rigidbody on one of the Cubes