Sphere sticks to cube

The problem: why does my sphere stick to the lower border after bouncing from the right border?

This problem always happens when ball.rigidbody.velocity.x != 0.

Update: I created a workaround which is shown below.

This is my simple scene (I removed all other parts to ensure that the bug doesn't relate to my code):

My Physic Material which I applied to both cuboids:

 Dynamic Friction:          0
 Static Friction:           0
 Bounciness:                1
 Friction Combine:          Minimum
 Bounce Combine:            Maximum
 Friction Direction 2:      0, 0, 0
 Dynamic Friction 2         0
 Static Friction 2:         0

I also created a behavior for the ball which basically sets rigidbody.velocity to an initial motion vector (say 3, -1, 0).

 Vector3 velo = rigidbody.velocity;
 string[] applicableBorders = new string[]{"BorderTop", "BorderBottom"};
 
 if (velo.x == 0 && System.Array.IndexOf(applicableBorders, collision.collider.name) < 0) {
   rigidbody.velocity = new Vector3(rigidbody.velocity.x, rigidbody.velocity.y * -1.0f, rigidbody.velocity.z);
 }

I wonder whether any cleaner solution exists.