Transform variable has not been assigned, but it has?

Hi all,

I'm working on getting the mechanics for a puzzle game to work. It's a basic lockpicking game and essentially I want the tumblers to move up after they have been hit in the correct order. This code is assigned to the lockpick, tumblers have separate scripts. I did choose the tumblers in the Unity menu for the Serialized fields. Here is the code:

    [SerializeField] private Transform transformTumbler1;
     [SerializeField] private Transform transformTumbler2;
     [SerializeField] private Transform transformTumbler3;
     [SerializeField] private Transform transformTumbler4;
     [SerializeField] private Transform transformTumbler5;
 
 void OnCollisionEnter2D(Collision2D collision)
     {
 
         Tumbler1 tumbler1 = collision.gameObject.GetComponent<Tumbler1>();
         Tumbler2 tumbler2 = collision.gameObject.GetComponent<Tumbler2>();
         Tumbler3 tumbler3 = collision.gameObject.GetComponent<Tumbler3>();
         Tumbler4 tumbler4 = collision.gameObject.GetComponent<Tumbler4>();
         Tumbler5 tumbler5 = collision.gameObject.GetComponent<Tumbler5>();
 
 
         if(tumbler1 != null)
         {   
             if(CheckTumbler(1, order, currentOrder))
             {
                 currentOrder++;
                 LockTumbler(1);
                 Debug.Log("Correct");         
             }
             else
             {
                 Debug.Log("Incorrect");
                 wrongAttempt++;
             }
         }
 
         if (tumbler2 != null)
         {
             if (CheckTumbler(2, order, currentOrder))
             {
                 currentOrder++;
                 LockTumbler(2);
                 Debug.Log("Correct");               
             }
             else
             {
                 Debug.Log("Incorrect");
                 wrongAttempt++;
             }
         }
 
         if (tumbler3 != null)
         {
             if (CheckTumbler(3, order, currentOrder))
             {
                 currentOrder++;
                 LockTumbler(3);
                 Debug.Log("Correct");      
             }
             else
             {
                 Debug.Log("Incorrect");
                 wrongAttempt++;
             }
         }
 
         if (tumbler4 != null)
         {
             if (CheckTumbler(4, order, currentOrder))
             {
                 currentOrder++;
                 LockTumbler(4);
                 Debug.Log("Correct");      
             }
             else
             {
                 Debug.Log("Incorrect");
                 wrongAttempt++;
             }
         }
 
         if (tumbler5 != null)
         {
             if (CheckTumbler(5, order, currentOrder))
             {
                 currentOrder++;
                 LockTumbler(5);
                 Debug.Log("Correct");
             }
             else
             {
                 Debug.Log("Incorrect");
                 wrongAttempt++;
             }
         }
     }
 
     bool CheckTumbler(int tumblerNumber, int[] order, int currentOrder)
     {
         if (tumblerNumber == order[currentOrder])
         {
             return true;
         }
         return false;
     }
 
     void LockTumbler(int tumblerNumber)
     {
 
         if (tumblerNumber==1)
         {
             transformTumbler1.position = transformTumbler1.position + new Vector3(-2.2f, 2.0f, 0.0f);
         }
 
         if (tumblerNumber ==2)
         {
 
             transformTumbler2.position = transformTumbler2.position + new Vector3(0.0f, 2.0f, 0.0f);
         }
 
         if (tumblerNumber ==3)
         {
             transformTumbler3.position = transformTumbler3.position + new Vector3(2.43f, 2.0f, 0.0f);
         }
 
         if (tumblerNumber ==4)
         {
             transformTumbler4.position = transformTumbler4.position + new Vector3(4.84f, 2.0f, 0.0f);
         }
 
         if (tumblerNumber ==5)
         {
             transformTumbler5.position = transformTumbler5.position + new Vector3(7.22f, 2.0f, 0.0f);
         }
     }