Custom Inventory dupes Items. Why? [SOLVED]

I have created a custom inventory this works very well, but now I wanted to make a system in which the item, for example, on slot 5 is moved to slot 4 if slot 4 is empty.

I've made a script that partially works, however, duplicates the script the item to be moved

Here is the script:

Local Script:

wait ()
while true do
    wait (1)
    local ID2Replace = 0
    local Slots = 0
    local ActiveSlot = game.Players.LocalPlayer.PlayerSystem.ActiveSlot.Value
    local SaveSlot = game.Players.LocalPlayer.PlayerSystem:FindFirstChild("SaveSlot"..ActiveSlot)
    if SaveSlot ~= nil then
        local SlotsLength = SaveSlot.Inventory.Bag1:GetChildren()
        repeat 
            Slots = Slots + 1
            local CurrentSlot = SaveSlot.Inventory.Bag1:FindFirstChild("SLOT"..Slots)
            if CurrentSlot.Value ~= "0, 0" then
                local Slot2Test = SaveSlot.Inventory.Bag1:FindFirstChild("SLOT"..Slots - 1)
                if Slot2Test ~= nil then
                    if Slot2Test.Value == "0, 0" and Slot2Test ~= nil then
                        Slot2Replace = Slots
                        local DataTable = {
                            ["OldSlot"] = CurrentSlot.Name,
                            ["NewSlot"] = Slot2Test.Name,
                            ["OldSlotValue"] = CurrentSlot.Value
                        }
                        game.Workspace.System.Events.ReplaceEvent:FireServer(DataTable)
                    end
                end
            end
        until Slot2Replace ~= 0 or Slots == #SlotsLength
    end
end

ServerScript:

script.Parent.Parent.Events.ReplaceEvent.OnServerEvent:Connect(function (Player, DataTable)
    local ActiveSlot = Player.PlayerSystem.ActiveSlot.Value
    local SaveSlot = Player.PlayerSystem:FindFirstChild("SaveSlot"..ActiveSlot)
    if SaveSlot ~= nil then

    local OldSlot = SaveSlot.Inventory.Bag1:FindFirstChild(DataTable["OldSlot"]) 
    local NewSlot = SaveSlot.Inventory.Bag1:FindFirstChild(DataTable["NewSlot"]) 
    if OldSlot ~= nil and NewSlot ~= nil then

    OldSlot.Value = "0, 0"
    NewSlot.Value = DataTable["OldSlotValue"]
    end
    end
end)

That solved the problem:

OldSlot.Value = "0, 1"
wait (1)
OldSlot.Value = "0, 0"