Roll a ball - Ball colliding between ground colliders

Hi,

I am trying to improve the tutorial Roll-a-ball (https://unity3d.com/pt/learn/tutorials/projects/roll-ball-tutorial) by adding new grounds (cubes with box collider) in runtime. The ball has the same components and the same values as the tutorial (a sphere with sphere collider and a rigidbody with default values). The problem is: even if there aren't any gap between the ground, the ball collides when it roll to a new ground and it gives a little jump. The colliders are perfectly aligned.

Did I make some mistake? Did I miss something?

Thanks in advance! =)