Mobile Gyro tilt game has collision and movement problems

I am working on a mobile game where the player can tilt a platform with a ball on it using their phone's gyroscope. (Think Monkey Ball but instead of being controlled with analog stick platform is controlled by tilting your phone)

The platform's rotation is set to the rotation of the phone's gyro, and the ball just has a rigidbody on it.

This works well until the ball goes near the edge of platform, where it runs into collision and movement issues (Ex. Ball falling when platform is tilted downward too fast)

Example: link text

(The ball ideally would not phase through the platform or have to fall when the platform is tilted downward.)

Any ideas on how to fix this?