How to reproduce:

1. Open attached project
2. Open scene playground.unity
- Scene contains a vehicle using 8 wheel colliders and a single box collider, as well as a plane to drive on and some road bumps
3. Play the scene
- Use WSAD to control the vehicle
4. Select the gameobject carRoot/Cube
5. Disable its Box Collider component
- Nothing happens, as expected
6. Enable it again
- If the vehicle was not moved, the wheel colliders should fall through the floor
- If the vehicle was moved and is now stationary, try moving it some more. Then note how the wheel colliders appear to be reacting to the box collider
- Setting up the wheels so they don't intersect with the box solves the issue