GameObject only spawning 60% of the time (c#)

I am currently working on my first unity game outside of a tutorial. I am trying to get a coin to spawn on the y axis at random positions. I have done this in c#, except the code only works some times (60% - 70% of the time). The other times the coin does not spawn and an error message saying NullReferenceException: Object reference not set to an instance of an object appears. Can you please help me.

Here is the scripts thats spawns the coin prefab:

 using UnityEngine;
 using System.Collections;
 
 public class CoinSpawner : MonoBehaviour {
 
     public GameObject Collectible;
 
     private float Miny = -2.6f;
     private float Maxy = 2.6f;
 
     // Use this for initialization
     void Start () {
         Debug.Log ("Called");
 
         spawnCoin ();
     }
      
     public void spawnCoin () {
         Vector3 coin = new Vector3 (-2.1f, Random.Range (Miny, Maxy),0);
         Instantiate (Collectible, coin, Quaternion.identity);
     }
     
     // Update is called once per frame
     void Update () {
     
     }
 }
 

Here is the script that tells the coin what to do once spawned:

 using UnityEngine;
 using System.Collections;
 
 public class CoinBehaviour : MonoBehaviour {
 
     public CoinSpawner coinSpawner;
     public int scoreValue = 1;
 
     public ScoreKeeper scoreKeeper;
 
     // Use this for initialization
     void Start () {
         // Get Score text thingy
         scoreKeeper = GameObject.Find ("0000").GetComponent<ScoreKeeper> ();
         // Get coin spawner thingy
         coinSpawner = GameObject.Find ("Spawner").GetComponent<CoinSpawner>();
     }
     
     void OnTriggerEnter2D (Collider2D col) {
 
         if (col.gameObject.tag == "Player") {
             Debug.Log ("Hit");
             Destroy (gameObject);
             coinSpawner.spawnCoin();
             scoreKeeper.Score(scoreValue);
     }
 
     
 }
 }

Picture of Game while working:

Picture of Game while not working: