Rigid Body not working correctly

Sorry for the vague title.

So i’m starting to experiment with physics, and so far so good, but i’m at a standstill about rigid bodies.

Basically there’s a ball on a plane with some side railings (both the plane and the railings are set to passive to be immobile)

the ball is floating above the railing (highest object) instead of being above the plane and moving within the width limit of the railings, pinball style.

test.blend (129 KB)

this is the effect im trying to achieve:

Hello and sorry for my poor english.
I applied the “Skin” modifier and changed the shape from “convex skull” to “mesh” on the railing, and it works.

Bye!