Ball passes through the floor on movement

First of all, I am sorry about the not very clear title, but I wasn't able to make the problem clear in few words! I am currently facing a very annoying problem: I have a ball with a RigidBody component and a Sphere Collider which lays down on a set of tiles that form a plane. Those tiles are all under a Pivot gameobject and all have a simple Mesh Collider. Whenever I try to rotate the pivot point to move the ball, instead of making the ball roll down, it goes through it. I thought this might happen because both colliders (tile on whic the ball is on and the sphere itself) are in the exact same location, but I didn't manage to fix it using only the inspector.

What am I missing? Am I right about what's causing the problem? and most important, how do I fix it?

I made a screencast to help you understand the problem, you can find it here.