Textures break when mesh stops sharing vertices

I have a program which stops a mesh sharing vertices in the editor. However when I run a process on a test (see below) the textures go all weird and all go onto certain part of the robot not the whole thing.

Here is my code:

void Process() {

         Transform curr = Selection.activeTransform;
         
         if (curr == null) {
             error = "Please select an appropriate object in the heirarchy";
             Debug.Log (error);    
             return;
         }
         
         MeshFilter meshFil;
         meshFil = curr.GetComponent<MeshFilter>();
         if (meshFil == null || meshFil.sharedMesh == null) {
             error = "No editable mesh filter is detected on selected object \n(" + curr.name + ")";
             Debug.Log (error);
             return;
         }
 
         GameObject gamObj = Instantiate (curr.gameObject) as GameObject;
         meshFil = gamObj.GetComponent<MeshFilter>();
         Mesh mesh = Instantiate (meshFil.sharedMesh) as Mesh;
         meshFil.sharedMesh = mesh;
         Selection.activeObject = gamObj.transform;
 
         Vector3[] oldVerts = mesh.vertices;
         int[] trigs = mesh.triangles;
         Vector3[] newVerts = new Vector3[trigs.Length];
         for (int i = 0; i < trigs.Length; i++) {
             newVerts[i] = oldVerts[trigs[i]];
             trigs[i] = i;
         }
         mesh.vertices = newVerts;
         mesh.triangles = trigs;
 
         mesh.RecalculateBounds();
         mesh.RecalculateNormals();
 }