FindFirstEmptySlotInBag not updating

Hey guys it's me again ;-)

I have some issues with the function FindFirstEmptySlotInBag(BAG_BACKPACK).

I want to move items from the bank into my inventory but it always just moves one item.
I dumped the values of the variables and found out that the Destination SlotID (slotId_Bag) always stays the same.
So I think that this is the issue - but unfortunately I cannot image why it is not updating because I call it in every loop of the for-loop so it should update correctly.

function LootManager.GetIngredientsFromBank()
    local name
    local item
    local slotId
    local count
    local bagId = BAG_BANK
    local slots = GetBagSize(bagId)
    local slotId_Bag
    local bag_Dest = BAG_BACKPACK
 
    for i=0, slots - 1 do
        slotId = i
        name = zo_strformat(SI_UNIT_NAME, GetItemName(bagId, slotId))
        item, count = GetItemInfo(bagId, slotId)
        slotId_Bag = FindFirstEmptySlotInBag(bag_Dest)
 
        if name == LootManager.savedVars.ingredient1 then
            LootManager.MoveItem(bagId, slotId, bag_Dest, slotId_Bag, count)
        end 
 
        if name == LootManager.savedVars.ingredient2 then   
            LootManager.MoveItem(bagId, slotId, bag_Dest, slotId_Bag, count)
        end 
        
        if name == LootManager.savedVars.ingredient3 then
            LootManager.MoveItem(bagId, slotId, bag_Dest, slotId_Bag, count)
        end 
 
    end
 
end
 
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function LootManager.MoveItem(srcBag, srcSlot, destBag, destSlot, quantity)
    ClearCursor()
    zo_callLater(function() 
        if CallSecureProtected("PickupInventoryItem", srcBag, srcSlot, quantity) then
            CallSecureProtected("PlaceInInventory",destBag, destSlot)
        end
    end, 500)   
    ClearCursor()   
    d("Moved: " .. zo_strformat(SI_UNIT_NAME, GetItemName(srcBag, srcSlot)) .. " x " .. quantity .. " to inventory")
    d("SrcBag: " .. srcBag .. " SrcSlot: " .. srcSlot .. " DestBag: " .. destBag .. " DestSlot: " .. destSlot .. " Quantity: " .. quantity)
end

Do you see any error here?

Thanks in advance