Problem with Collider wont appear

Unity Engine
1 
using UnityEngine;
using System.Collections;

public class hitBySpell : MonoBehaviour {
    public float Health = 100;
    public GameObject Target;
    // Use this for initialization
    void Start () {
        Target = GameObject.FindWithTag ("Player");
    }
   
    // Update is called once per frame
    void Update () {

        transform.LookAt (Target.transform); // It happends right here

    if(Health <= 0){
            Destroy (gameObject);
        }
    }

    void OnTriggerEnter2D (Collider2D hit)
    {
        if (hit.gameObject.tag == "damageFireball") {
            Health -= 50;
            Debug.Log(Health);
        }
    }
}

Why is that when i include this code " transform.LookAt (Target.transform) ", then this problem (See attached file).

But as soon i remove the code, i dont get the problem

2210753--147023--unity.png

2

How small is the fireball GameObject?
What this problem seems to be, is that either the object detecting the collision, or the fireball has a collider that is too small.

3

Its not about the fireball GameObject

The script above is attached to af 3D gameobject, with a 2D Box Collider.

As soon the Lookat part is include, the error come, as in the attached picture

4

The error seems quite clear on what’s wrong. What is the scale of your GameObjects and how small are the models you’re importing?