Why doesn't my combined mesh look how it supposed to do?

I have a script that generates all necessary quads and it works fine. The picture below shows the separate quads before combining:

After that i'm combining everything with this function:

 void combineQuads()
 {
     MeshFilter[] meshFilters = GetComponentsInChildren<MeshFilter>();
     CombineInstance[] combine = new CombineInstance[meshFilters.Length];
     for (int i = 0; i < meshFilters.Length; i++)
     {
         combine[i].mesh = meshFilters[i].sharedMesh;
         combine[i].transform = meshFilters[i].transform.localToWorldMatrix;
     }
 
     MeshFilter mf = (MeshFilter)this.gameObject.AddComponent(typeof(MeshFilter));
     mf.mesh = new Mesh();
     mf.mesh.CombineMeshes(combine);
 
     MeshRenderer renderer = this.gameObject.AddComponent(typeof(MeshRenderer)) as MeshRenderer;
     renderer.material = material;
 
     foreach (Transform quad in this.transform)
     {
             Destroy(quad.gameObject);
     }
 }

And then i get this:

Why does this happen? If i generate a way smaller chunk everything is working fine but the larger ones are glitching. It confuses me.