How do I fix the swapping function for my Inventory system?

I've been working on an inventory system for a survival game I've been working on, and I've been having trouble with it. I've been lately working specifically on the swapping function, where you can select an item, press a button, and then if you press 1 for example, the selected item will go in slot 1 of the hotbar. However, when I programmed the code for the swapping to actually happen, it didn't work. I believe it was due to the updateDisplay function and how it works, since the item's data was still in the hotbar slot.

Code is below (go to lines 116 and 188 ):

local StarterGui = game:GetService("StarterGui")
local Players = game:GetService("Players")
local UIS = game:GetService("UserInputService")

StarterGui:SetCoreGuiEnabled(Enum.CoreGuiType.Backpack, false)

local player = Players.LocalPlayer
local backpack = player.Backpack
local char = player.Character

local GUI = script.Parent.Parent.Inventory
local hotbar = GUI.Hotbar
local inventory = GUI.Inventory
local items = inventory.Items

local tooltip = inventory.Tooltip
local itemNameT = inventory.Tooltip.ToolName
local itemDescription = inventory.Tooltip.Tooltip

local slot1 = inventory.Items.InventorySlot1
local slot2 = inventory.Items.InventorySlot2
local slot3 = hotbar.Frame.HotbarSlot1
local slot4 = hotbar.Frame.HotbarSlot2
local openButton = hotbar.OpenInventory
local equipButton = inventory.EquipHotbarButton

local unselctedColor = Color3.fromRGB(121, 121, 121)
local selectedColor = Color3.fromRGB(62, 62, 62)

local selectedSlot = nil


local invSlotData = {
    [slot1] = nil,
    [slot2] = nil   
}

local hotbarSlotData = {
    [slot3] = nil,
    [slot4] = nil
}

local function scanItems()

    local items = {}

    --checks backpack and character for items and adds them to the Items table
    for i, tool in pairs(backpack:GetChildren()) do
        if tool.ClassName == "Tool" then
            table.insert(items, tool)
        end
    end

    for i, tool in pairs(char:GetChildren()) do
        if tool.ClassName == "Tool" then
            table.insert(items, tool)
        end
    end


    local invItems = {}

    --[[looks through Items table, and if a tool has the same name as an index in invItems table, add to the index's count and insert
    the tool's name into the index's Items table. else, create a new index with the tool's name and set all it's tables to default  --]]
    for i, tool in pairs(items) do
        if invItems[tool.Name] then
            invItems[tool.Name].Count += 1
            table.insert(invItems[tool.Name].Items, tool)

        else
            invItems[tool.Name] = {
                Count = 1,
                Items = {tool}
            }
        end
    end

    return invItems
end

local function resetItems()
    for i, button in pairs(items:GetChildren()) do
        if button.ClassName == "ImageButton" then
            button.Image = ""
            button.CountDisplay.Text = ""
            button.BackgroundColor3 = Color3.fromRGB(255, 255, 255)
        end
    end

    for i, button in pairs(hotbar.Frame:GetChildren()) do
        if button.ClassName == "ImageButton" then
            button.Image = ""
            button.CountDisplay.Text = ""
            button.BackgroundColor3 = Color3.fromRGB(255, 255, 255)
        end
    end
end

local function updateSelected(selectedItem, toolData)
    --checks all buttons in items frame and resets all background colors to default except sample


    --[[  selectedItem's background color is changed to selectedColor and selectedSlot is set to toolData.
    selectedItem's name and tooltip is pulled from toolData and used for tooltip in inventory.--]]
    selectedSlot = toolData


    itemNameT.Text = toolData.Items[1].Name
    itemDescription.Text = toolData.Items[1].ToolTip
end


--UPDATE DISPLAY FUNCTION IS HERE, CHECK THIS OUT IF YOURE FIXING SCRIPT


local function updateDisplay()
    resetItems()

    local invItems = scanItems()
    local connection = nil
    local equipButtonConnection = nil


    for toolName, toolData in pairs(invItems) do
        if invSlotData[slot1] == nil or toolData.Items[1].Name == invSlotData[slot1].Items[1].Name then

            invSlotData[slot1] = toolData

            slot1.CountDisplay.Text = toolData.Count
            slot1.Image = toolData.Items[1].TextureId



            connection = slot1.MouseButton1Click:Connect(function()
                updateSelected(slot1, toolData)
            end)

        elseif invSlotData[slot2] == nil or toolData.Items[1].Name == invSlotData[slot2].Items[1].Name then


            invSlotData[slot2] = toolData

            slot2.CountDisplay.Text = toolData.Count
            slot2.Image = toolData.Items[1].TextureId



            connection = slot2.MouseButton1Click:Connect(function()
                updateSelected(slot2, toolData)
            end)

        elseif hotbarSlotData[slot3] == nil or toolData.Items[1].Name == hotbarSlotData[slot3].Items[1].Name then


            hotbarSlotData[slot3] = toolData

            slot3.CountDisplay.Text = toolData.Count
            slot3.Image = toolData.Items[1].TextureId



            connection = slot3.MouseButton1Click:Connect(function()
                updateSelected(slot3, toolData)
            end)


        elseif hotbarSlotData[slot4] == nil or toolData.Items[1].Name == hotbarSlotData[slot4].Items[1].Name then

            hotbarSlotData[slot4] = toolData

            slot4.CountDisplay.Text = toolData.Count
            slot4.Image = toolData.Items[1].TextureId


            connection = slot4.MouseButton1Click:Connect(function()
                updateSelected(slot4, toolData)
            end)

        end

    end

end

--SWAPPING ITEMS FUNCTION IS ALSO HERE


local equipButtonDebounce = false

local keysToSlots = {
    [Enum.KeyCode.One] = slot3,
    [Enum.KeyCode.Two] = slot4,
}

local function swapItemSlots()

    if selectedSlot == nil or equipButtonDebounce == true then
        equipButton.Text = "Can't Equip to Hotbar"
        wait(1)
        equipButton.Text = "Equip to Hotbar"

        return
    end

    equipButtonDebounce = true

    equipButton.Text = "Press a Number 1-2"

    local input, gameProcessedEvent = UIS.InputBegan:Wait()

    equipButton.Text = "Equip to Hotbar"



    local chosenHotbarSlot = nil

    for keycode, slot in pairs(keysToSlots) do
        if input.KeyCode == keycode then
            chosenHotbarSlot = slot
            break
        end
    end

    if chosenHotbarSlot == nil then
        equipButton.Text = "Wrong Button!"

        task.wait(1)

        equipButton.Text = "Equip to Hotbar"
    else
        for slotF, itemData in pairs(hotbarSlotData) do
            if itemData.Items[1].Name == selectedSlot.Items[1].Name then
                hotbarSlotData[slotF] = nil
                print(hotbarSlotData)
            end

        end

        hotbarSlotData[chosenHotbarSlot] = selectedSlot
        selectedSlot = nil
        updateDisplay()


        print(chosenHotbarSlot)
        print(invSlotData)
        print(hotbarSlotData)
    end

    equipButtonDebounce = false

end

equipButton.MouseButton1Click:Connect(swapItemSlots)




task.spawn(function()
    while true do
        wait(1)
        updateDisplay()
    end
end)