My Load function isn't working and now I'm getting an error..

I have a Save Manager set up to save 3 different stats on two characters. 2 sets of in hand objects, 2 sets of inventory's and a chest management.
The chest management and the in hand objects seem to save and load fine, however the inventory doesn't. Originally my chest wasn't saving properly and I was getting the following error "InvalidOperationException: Collection was modified; enumeration operation may not execute." after a brief search this lead me to add .ToArray() to line 85 of my code. This fixed the chest however the inventory still didn't want to play ball.

I was then receiving no error of any kind and had tried rebooting etc. I then decided to remove the script from the game object and reattach it and am now getting the following error "NullReferenceException: Object reference not set to an instance of an object SaveManager+c__Iterator0.MoveNext () (at Assets/Scripts/SaveManager.cs:57) UnityEngine.MonoBehaviour:StartCoroutine(String) SaveManager:Awake() (at Assets/Scripts/SaveManager.cs:24)"

The lines mentioned in the errors are below along with a link to the entire script.

Original error:

         foreach(SerializableCheset sc in chests.ToArray())
         {
                 while (!GameManager.Instance.FindChestWithID (sc.ID).HasGenerated)
                 {
                         yield return new WaitForEndOfFrame();
                 }
                 GameManager.Instance.FindChestWithID(sc.ID).LoadItems (sc._MyItemsString);
         }

New error, lines 21- 25:

    void Awake()
     {
             Instance = this;
             StartCoroutine("Load");
     }

New error lines 52-57:

 public IEnumerator Load()
 {
         byte[] b = File.ReadAllBytes (Application.persistentDataPath + path);
         List<object> o = DeSerialize (b);
  
          p1_Hand = GameManager.Instance.FindItem ((string)o[0]);

for the entire script please use this link Script

Thank you for any assistance you might be able to give.