Skinned Mesh bug while assigning new bones

Hello. I've made a shirt for my character which is basically the same vertices as in the character model but without the unnecessary faces (like legs, head, etc.) - it has the identical rig, weights setup and it's in .blend format.

Now I put it inside of my player model, positioned it and applied a script that assigns it the bones of my character so it animates along with it but the thing is that it gets all messed up.

.

This is how it looks like in pause mode:

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And this is what happens in play mode:

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Here's how I setup the new bones:

 public class BoneReplacer : MonoBehaviour 
 {
     public GameObject target;
     SkinnedMeshRenderer myRenderer;
     Transform[] newBones;
     SkinnedMeshRenderer targetRenderer;
     Dictionary<string, Transform> boneMap = new Dictionary<string, Transform>();
 
     void Start()
     {
         targetRenderer = target.GetComponent<SkinnedMeshRenderer>();
 
         foreach(Transform bone in targetRenderer.bones)
         {
             boneMap[bone.gameObject.name] = bone;
         }
 
         myRenderer = gameObject.GetComponent<SkinnedMeshRenderer>();
         newBones = new Transform[myRenderer.bones.Length];
 
         for(int i = 0; i < myRenderer.bones.Length; i++)
         {
             GameObject bone = myRenderer.bones[i].gameObject;
             if(!boneMap.TryGetValue(bone.name, out newBones[i]))
             {
                 Debug.Log("Unable to map bone ~" + bone.name + "~ to target skeleton!");
                 break;
             }
         }
 
         myRenderer.bones = newBones;
     }
 }

.

Generally everything is animating fine, bones are following the animation just right but as you can see the mesh is a mess. Does anyone of you know of any solution to this problem? I'd be very grateful for one!