IDropHandler only getting called when flicking the mouse

I am using an IDropHandler for a drag and drop system. I tested the Idrophandler and the drop method only calls if I flick my mouse or I move my mouse really fast. If I move my mouse slowly, it doesn't work. I followed a tutorial by kryzarel and his code seemed to work completely fine.`private void Drop(BaseItemSlot dropItemSlot) { if (dragItemSlot == null) return;

     if (dropItemSlot.CanAddStack(dragItemSlot.Item))
     {
         AddStacks(dropItemSlot);
     }
     else if (dropItemSlot.CanReceiveItem(dragItemSlot.Item) && dragItemSlot.CanReceiveItem(dropItemSlot.Item))
     {
         SwapItems(dropItemSlot);
     }
     EndDrag(dropItemSlot);
 }`

private void SwapItems(BaseItemSlot dropItemSlot) { EquippableItem dragEquipItem = dragItemSlot.Item as EquippableItem; EquippableItem dropEquipItem = dropItemSlot.Item as EquippableItem;

     if (dropItemSlot is EquipmentSlot)
     {
         if (dragEquipItem != null) dragEquipItem.Equip(this);
         if (dropEquipItem != null) dropEquipItem.Unequip(this);
     }
     if (dragItemSlot is EquipmentSlot)
     {
         if (dragEquipItem != null) dragEquipItem.Unequip(this);
         if (dropEquipItem != null) dropEquipItem.Equip(this);
     }
     statPanel.UpdateStatValues();

     Item draggedItem = dragItemSlot.Item;
     int draggedItemAmount = dragItemSlot.Amount;

     dragItemSlot.Item = dropItemSlot.Item;
     dragItemSlot.Amount = dropItemSlot.Amount;

     dropItemSlot.Item = draggedItem;
     dropItemSlot.Amount = draggedItemAmount;

 }

 private void AddStacks(BaseItemSlot dropItemSlot)
 {
     int addableAmount = dropItemSlot.Item.MaxStackSize - dropItemSlot.Amount;
     int stacksToAdd = Mathf.Min(addableAmount, dropItemSlot.Amount);

     dropItemSlot.Amount += stacksToAdd;
     dragItemSlot.Amount -= stacksToAdd;
 }