Removing method from OnRightClickEvent

Hi,

I am making an inventory system for a 2D game. I have some functionality that runs a method when right-clicking on an "item slot".

However, sometimes I want something else to happen when right-clicking. In this case, I want to transfer items to a chest when the chest is open.

In my ItemSlot script, I listen for OnPointerClick() and check if it was a right-click:

 public event Action<ItemSlot> OnRightClickEvent;
 
 public void OnPointerClick(PointerEventData eventData)
 {
     if (eventData != null && eventData.button == PointerEventData.InputButton.Right)
     {
         if (OnRightClickEvent != null)
         {
             OnRightClickEvent(this);
         }
     }
 }

In my ItemContainer (inventory) script, I set it up:

 public event Action<ItemSlot> OnRightClickEvent;
 
 protected virtual void Awake()
 {
     for (int i = 0; i < itemSlots.Count; i++)
     {
         itemSlots[i].OnRightClickEvent += slot => OnRightClickEvent(slot);
     }
 }

And in my InventoryManager, I assign a method that runs every time I click on an "item slot" in the inventory:

 private void Awake()
 {
     inventory.OnRightClickEvent += InventoryRightClick;    
 }
 private void InventoryRightClick(ItemSlot itemSlot)
 {
      //do something
 }

Also in the same script, I sometimes run this code to switch the method I am running when a right-click occurs:

 public void OpenItemContainer(ItemContainer itemContainer)
 {
     inventory.OnRightClickEvent -= InventoryRightClick;
     inventory.OnRightClickEvent += TransferToItemContainer;
 }
 
 private void TransferToItemContainer(ItemSlot itemSlot)
 {
     //do something else
 }

The problem is that this last part doesn't work. When I run the OpenItemContainer() method, and then proceed with right-clicking on an "item slot", I just end up running both methods.

In other words, this doesn't work:

 inventory.OnRightClickEvent -= InventoryRightClick;

Does anyone know why? Thanks, in advance!