A question about continuous collision detection and bounce off wall

I created a sphere and a wall using box. They all have rigidbody and the wall has IsKinematic set to true. It is said that fast moving objects should use 'Continuous Dynamic' collision checking method, and I do have set the sphere to 'Continuous Dynamic' and the wall to 'Continuous'. However, when sphere gained enough velocity, the sphere sometimes just crashed into the wall and sticked into it instead of bouncing off. Am I doing something wrong? Please help. Thanks. (I move the ball by changing global gravity.)