I ran into some problems with my combined Meshes getting scaled to zero using Mesh.CombineMeshes().

I was calling:

```
CombineInstance instance = new CombineInstance();
instance.transform.SetTRS(Vector3.zero, Quaternion.identity, Vector3.one);
Debug.Log(instance.transform);
```

and getting an output of:

```
[0,0,0,0,
0,0,0,0,
0,0,0,0,
0,0,0,0]
```

However, I found that if I called:

```
Matrix4x4 matrix = new Matrix4x4();
matrix.SetTRS(Vector3.zero, Quaternion.identity, Vector3.one);
Debug.Log(matrix);
```

I would get the correct result of:

```
[1,0,0,0,
0,1,0,0,
0,0,1,0,
0,0,0,1]
```

I could then store matrix in the transform on the CombineInstance and get the correct result. (My full code pulls from a TRS on a ScriptableObject. The “Vector3.zero, Quaternion.identity, Vector3.one” was for testing purposes.)

So I basically resolved my own problem.

My main question is: Why am I getting different results with what I assumed is the same function? Is this some sort of initialization problem on CombineInstance.transform? Is it a bug?