Physics problems after scaling the map

Hi, I have a doubt.
I tried to scale the meshes of a project (from 1 to 0.3) and when the car proceeds on the main road (made through the use of splines) it occasionally has few clicks, as if it encounters an obstacle.

I have tried to check several times but there is nothing particular along the path (I have also removed the collisions from everything that is not essential) and when I activate show collision it still shows nothing strange on the road!

Thanks in advance for the help