Camera Bug

public class CameraController : MonoBehaviour {

    public GameObject target;
    public float rotateSpeed;
    Vector3 offset;

    void Start() {
        offset = target.transform.position - transform.position;
    }

    void LateUpdate() {
        float horizontal = Input.GetAxis("Mouse X") * rotateSpeed;

        target.transform.Rotate(0, horizontal, 0);

        float desiredAngle = target.transform.eulerAngles.y;
        Quaternion rotation = Quaternion.Euler(0, desiredAngle, 0);
        transform.position = target.transform.position - (rotation * offset);

        transform.LookAt(target.transform);
    }
}