Issue with mesh collider

Hi guys
I have a mesh collider on a mountain i created in blender. But when i try walk on it i go right through and then can't go back out as the mesh collider prevents it. What would cause a mesh collider to only work for one side of a mesh?If i change it to convex then it stops both sides but can't have it as convex.

 

Was it always only 1 sided i could have sworn with unity 4 it swung both ways?Is that just my memory turning tricks?

Well that sucks I have the shader set to double sided guess that does not matter. Have to redo the mesh nowThx for the reply

 

(Old thread, but I stumbled upon it via Google)

Since Unity 5.5, there is this: https://docs.unity3d.com/ScriptReference/Physics-queriesHitBackfaces.html

 

doesn't work for me, I can yet walk through mesh colliders