Mesh Collider works only sometimes

Why does this Mesh Collider only works when its deactivated in void Awake() and reactivated in Start()?
I tried to generate Terrain and i found out if i add the Mesh Collider right in the beginning its works just fine but if i place it after the math for the height calculation i must reactivate it in Start(). (Code is to long for here)

Code (CSharp):

1. using UnityEngine;
2.  
3. public class Test : MonoBehaviour
4. {
5.     void Awake()
6.     {
7.         Mesh mesh = new Mesh();
8.         Vector3[] vertices = new Vector3[3];
9.  
10.         vertices[0] = new Vector3(0, 0, 0);
11.         vertices[1] = new Vector3(0, 0, 10);
12.         vertices[2] = new Vector3(10, 0, 10);
13.  
14.  
15.         int[] triangles = { 0, 1, 2 };
16.  
17.  
18.         gameObject.AddComponent<MeshFilter>().mesh = mesh;
19.         gameObject.AddComponent<MeshCollider>()/*.enabled = false*/;
20.         gameObject.AddComponent<MeshRenderer>();
21.  
22.  
23.  
24.         mesh.vertices = vertices;
25.         mesh.triangles = triangles;
26.         mesh.RecalculateNormals();
27.  
28.         GameObject cube = GameObject.CreatePrimitive(PrimitiveType.Cube);
29.         cube.transform.position = new Vector3(2.5f, 3, 7);
30.         cube.AddComponent<Rigidbody>();
31.     }
32.  
33.     void Start()
34.     {
35.         //gameObject.GetComponent<MeshCollider>().enabled = true;
36.     }
37. }
38.  

 

After editing your mesh try to call mesh.UploadMeshData. It should fix having to deactivate and activate the Mesh Collider component which uses the edited mesh.