Why am I getting a nil value in UserInputService?

I'm about to pull my hair out trying to figure this out but I'm making a QTE (Quick Time Event) module that is using UserInputService.

The main function calls up the UI and hooks up a timer, variables, and a few conditional statements to BindToRenderStep and unbinds when the user fails to press the correct button, runs out of time, or completes the QTE. One of those variables is the current key the user must press, however past the first function call, my logic checking if the user is pressing the correct key outputs the current key being nil but somehow fires both conditions.

I printed out the current key and the amount as sanity checks to make sure it was updating on every frame and resetting upon the next call and everything looks to be okay, but my UserInputService logic says otherwise.

Note: UserInputService is hooked up outside BindToRenderStep and animations are synchronized.

Error: (It's line 084 in snippet) Players.veeplerthekrim.PlayerScripts.QTES:172: invalid argument #2 (string expected, got nil)

Module Code Snippet:

local result

function QTES.ShowQTE(period, keys)
	
	if playing == true then
		warn("Cannot interupt current QTE. Wait until this QTE is finished.")
		return
	end
	
	-- If no args
	if not period then
		period = 5
	end
	
	if not keys or not keys[1] then
		local r = {"Z", "X", "N", "M"}
		keys = {}
		for _ = 1, math.random(2,6) do
			keys[#keys + 1] = r[math.random(1,4)]
		end
	end
	
	local oldperiod = period
	local db = false
	local count = 1
	local currentkey = keys[count]
	local fail = false
	
	-- Start init QTES
	playing = true
	
	-- Create Keys icons for player to press
	CreateKeys(keys)


	print(#keys)
	takeControl()
	fadeinMenu()
	
	
	local function clearKeys()
		for _,v in pairs(QTEmenu.QTE_order:GetChildren()) do
			if v:IsA("ImageLabel") then v:Destroy() end
		end
	end

	-- Frame Check: Unbind if failed, when time runs out, or when currentkey = nil
	RS:BindToRenderStep("QTETimer", Enum.RenderPriority.Input.Value - 1, function(delta)
		period -= delta
		QTEmenu.Timer.bar.Size = UDim2.new(period/oldperiod,0,0.9,0)
	
		currentkey = keys[count]
		print("Current Key = ", currentkey)
		
		-- success case
		if currentkey == nil then 
			RS:UnbindFromRenderStep("QTETimer")
			Context_act:UnbindAction("freezeAction")
			QTEmenu.Enabled = false
			playing = false
			
			clearKeys()
			result = true 
		end
		
		-- fail case
		if period <= 0 or fail == true then
			QTEmenu.Timer.bar.Size = UDim2.new(0,0,0.9,0)
			RS:UnbindFromRenderStep("QTETimer")
			Context_act:UnbindAction("freezeAction")
			failedAnimation()
			QTEmenu.Enabled = false
			playing = false
			
			clearKeys()
			result = false
		end
	end)
	
	
	UIS.InputEnded:Connect(function(key)
		
		if playing == true and db == false and key.UserInputType == Enum.UserInputType.Keyboard then
			if key.KeyCode ~= Enum.KeyCode[currentkey] then
				db = true	
				fail = true
				failedAnimation()
				QTEmenu.Enabled = false
				clearKeys()
				db = false
			elseif key.KeyCode == Enum.KeyCode[currentkey] then
				print(count)
				db = true
				gotKeyCorrectEffect(QTEmenu.QTE_order["_"..count])
				count += 1
				wait(0.1)
				db=false
			end
		end
	end)
	
end

return QTES

Local Script:

local QTES = require(script.Parent)

QTES.ShowQTE(4, {"Z","X","Z"})
wait(5)
QTES.ShowQTE(4, {"Z","M","N"})

I don't think Enumerations can be accessed by integers. Although Enums have .Name and .Value properties, so you can try this with .Value.

(line 84):

            if key.KeyCode.Value ~= currentkey then

(line 91):

            elseif key.KeyCode.Value == currentkey then

I got it. Found out that each time I called my function, I was making a new connection with UserInputService, which was tracking old variables in memory. The only thing I had to do was disconnect my function.