Terrain heightmap resolution affects collision calculation

Hello,

I generated my terrain from a .raw file which has 2049x2049 resolution. When I set the terrain width,height to 300 my capsule colliders with rigidbodies falls a little through terrain then collision occurs and some of them start to bounce.

Is generating collider for terrain not working well when the width, heigth value of the terrain is much smaller then the heightmap value, which is 2049 since I imported that size of raw file? Because when I increase the width, height value problem goes away.

I also print message when collision occured as you can see it occurs when bottom circle goes into terrain and after that it starts to bounce.

One more info: This problem started to happen after upgrading my unity from 5.0.1 to 5.1.1.

Thank you very much!