Raycast returns Bad Triangle Index after delete triangles in mesh

Hi,

I generate a mesh with many triangles. I want to delete 2 triangles if i click them. It works the first time, but if i try to hit the next triangle.. the raycast triangleindex give me some wrong values.

1. i select a triangle, detect the triangle to get the quad and i remove it. http://www.terabyte-unlimited.com/help1.png

I remove the triangles from the Mesh an safe ist

  public static void RemoveFace(GameObject ga, int tIndex)
     {
         Mesh tmpMesh = ga.GetComponent<MeshFilter>().mesh;
         MeshCollider tmpCol = ga.GetComponent<MeshCollider>();
 
 
         Vector3[] vertices = tmpMesh.vertices;
         Vector2[] uv = tmpMesh.uv;
         int[] triangles = tmpMesh.triangles;
 
 
         Vector3[] nVertices = new Vector3[vertices.Length - 4];
         Vector2[] nUV = new Vector2[nVertices.Length];
         int[] nTriangles = new int[triangles.Length - 6];
 
 
         int iC = 0;
         int[] TriIndex = new int[6];
         /*
         TriIndex[0] = triangles[tIndex * 3 + 0];
         TriIndex[1] = triangles[tIndex * 3 + 1];
         TriIndex[2] = triangles[tIndex * 3 + 2];
         if ((float)tIndex / 2.0f - Mathf.Floor((float)tIndex / 2.0f) > 0.0f)
         {
             TriIndex[3] = triangles[(tIndex - 1) * 3 + 0];
             TriIndex[4] = triangles[(tIndex - 1) * 3 + 1];
             TriIndex[5] = triangles[(tIndex - 1) * 3 + 2];
         }
         else
         {
             TriIndex[3] = triangles[(tIndex + 1) * 3 + 0];
             TriIndex[4] = triangles[(tIndex + 1) * 3 + 1];
             TriIndex[5] = triangles[(tIndex + 1) * 3 + 2];
         }
 
         for (int i = 0; i < vertices.Length; i++)
         {
             if (!TriIndex.Contains<int>(i))
             {
                 nVertices[iC] = vertices[i];
                 nUV[iC] = uv[i];
                 iC++;
             }
         }
          * */
 
 
         TriIndex[0] = tIndex * 3 + 0;
         TriIndex[1] = tIndex * 3 + 1;
         TriIndex[2] = tIndex * 3 + 2;
         if ((float)tIndex / 2.0f - Mathf.Floor((float)tIndex / 2.0f) > 0.0f)
         {
             TriIndex[3] = (tIndex - 1) * 3 + 0;
             TriIndex[4] = (tIndex - 1) * 3 + 1;
             TriIndex[5] = (tIndex - 1) * 3 + 2;
         }
         else
         {
             TriIndex[3] = (tIndex + 1) * 3 + 0;
             TriIndex[4] = (tIndex + 1) * 3 + 1;
             TriIndex[5] = (tIndex + 1) * 3 + 2;
         }
 
         iC = 0;
         for (int i = 0; i < triangles.Length; i++)
         {
             if (!TriIndex.Contains<int>(i))
             {
                 nTriangles[iC] = triangles[i];
                 iC++;
             }
         }
 
 
 
         tmpMesh.Clear();
         tmpMesh.vertices = vertices;
         tmpMesh.triangles = nTriangles;
         tmpMesh.uv = uv;
         tmpMesh.Optimize();
         tmpMesh.RecalculateNormals();
 
         tmpCol.sharedMesh = tmpMesh;
     }

The two triangles are vanish.. all fine.. http://www.terabyte-unlimited.com/help2.png

If i try to raycast the next triangle, then i get some wrong triangleindex From the cast. http://www.terabyte-unlimited.com/help3.png

What can i do to get the right Triangle? Something wrong with the mesh? Or with my Raycast?