Instance:IsA randomly stopped working? [FIXED]

So, I'm trying to make a script that whenever somebody clicks two buttons they can insert a name to create another. I had no trouble with the script until randomly one line stopped working. I didn't change anything from the script, and all the line does is check if v is a frame. I have no idea what's causing this. Here's the script (Btw its a local script):

local filterd = game.ReplicatedStorage.Filter
local fil = game.ReplicatedStorage.FilterBack
local check = game.ReplicatedStorage.Send2
local server = game.ReplicatedStorage.ServerCreate
local counter = 0
local precheck = false
local id
local id2
local check = game.StarterGui.Main.Scroll:GetChildren()
local fail = game.ReplicatedStorage.Fail
local success = game.ReplicatedStorage.Success
local player = game.Players.LocalPlayer
local newgui = player:WaitForChild("PlayerGui"):WaitForChild("Request").TextBox
local debounce = false
check.OnClientEvent:Connect(function(button)
counter = counter + 1
	if counter == 1 then
	id = button.Parent.ID.Value
	else	
	id2 = button.Parent.ID.Value
		counter = 0
		for i, v in pairs(game.StarterGui.Main.Scroll:GetChildren()) do
			if v:IsA("Frame") then --this isnt the problem line, its farther down
				if v.ID.Value == id + id2 then
				if player.PlayerGui.Main.Scroll:FindFirstChild(v.Name) then
						v:Destroy()
					end	
					debounce = true	
					local guiclone = v:Clone()
					guiclone.Parent = player.PlayerGui.Main.Scroll
					success:Play()
						
					end
				end	
			if not debounce then	
			debounce = true			
				if v:IsA("Frame") then --problem line
					if v.ID.Value ~= id + id2 then
				if #game.StarterGui.Main.Scroll:GetChildren() - 1 <= #player.PlayerGui.Main.Scroll:GetChildren() - 1 then			
				fail:Play()
				newgui.Visible = true
					newgui.Parent.TextButton.Visible = true
				
				newgui.Parent.TextButton.MouseButton1Click:Connect(function()
					filterd:FireServer(newgui.Text)
					fil.OnClientEvent:Connect(function(filtered)
					newgui:ReleaseFocus()	
					local createserverelement = server:InvokeServer(filtered, id, id2)	
					if createserverelement == true then
							
					newgui.Text = ""
						newgui.Visible = false
							newgui.Parent.TextButton.Visible = false
								success:Play()
										wait()
											debounce = false
										else
											if player.PlayerGui.Main.Scroll:FindFirstChild((tostring(filtered))) then
												newgui.Visible = false
												newgui.Parent.TextButton.Visible = false
												fail:Play()
										end
									end
								end)
							end)
						end
					end
				end
			end
		end
	end
end)

So if you could help, I would appreciate it!

Turns out that line wasn't actually the culprit. It was the other Isa. I had to change that if from an end directly there to an else.