Not detecting collision on imported (DAE) objects?

Hi, I am trying to import an object (namely a road) to Unity. I design it in SolidWorks, save as .STL, then convert to DAE in MeshLab, and import it into Unity.

I choose "generate colliders" on import settings window. So it works normally, I mean, my character can go on it, and detect collisions, except when it is too fast.

When my character is too fast, the collision is not detected and I go through the object, thus fall to infinity.

What could be the problem? What can I do to avoid it?

Thanks !