ZIndex is broken?

I have a TeamSelect GUI and an Intro GUI, but for some reason, the TeamSelect GUI (ZIndex 9) always appears over the top of the Intro GUI (ZIndex 10). Why is this happening?

Intro GUI: http://puu.sh/jdnGO/10fcaa93fe.png

function added(player)
	local NameOfGame = "Roblox Prison" -- For future-proofing
	
	local GUI = script.IntroGUI:clone()
	GUI.Parent = player:WaitForChild("PlayerGui")
	
	local ThisFrame = GUI.Frame
	local Text = ThisFrame.TextLabel
	local ClassicLoad = ThisFrame.ClassicLoadFrame
	local LoadText = ClassicLoad.LoadText
	
	Text.Visible = false -- Prepare for it to fade in
	
	repeat wait() until player.Character
	
	Text.TextTransparency = 1
	Text.Text = NameOfGame
	Text.Visible = true
	wait(5)
	while Text.TextTransparency > 0 do
		Text.TextTransparency = Text.TextTransparency - .05 -- Fade it in
		wait(.05)
	end
	wait(5)
	ThisFrame.Visible = false
end
game.Players.PlayerAdded:connect(added)

TeamSelect GUI: http://puu.sh/jdnJR/1e8f5eceaf.png

local player = game.Players.LocalPlayer -- assign a variable to the local player
frame = script.Parent.Frame
GuardButtonShake = 0
InmateButtonShake = 0
CivilianButtonShake = 0

local function getTeamPlayers(teamColor)
local output = {}
for _, v in pairs(game.Players:getPlayers()) do
if (not v.Neutral) and v.TeamColor == BrickColor.new(teamColor) then
table.insert(output, player)
end
end
return output
end

local function GuardJoin()
    if (#getTeamPlayers("Bright blue")) < 15 then
        if player.Neutral then
            player.Neutral = false
        end
		player.TeamColor = BrickColor.new("Bright blue")
		frame.Visible = false
	else
		if GuardButtonShake == 0 then
			frame.GuardJoin.BackgroundColor3 = Color3.new(170, 0, 0)
			wait (0.3)
			frame.GuardJoin.BackgroundColor3 = Color3.new(12, 66, 0)
			wait (0.2)
			frame.GuardJoin.BackgroundColor3 = Color3.new(170, 0, 0)
			wait (0.1)
			frame.GuardJoin.BackgroundColor3 = Color3.new(12, 66, 0)
		end
    end
end

local function InmateJoin()
    if (#getTeamPlayers("Medium stone gray")) < 25 then
        if player.Neutral then
            player.Neutral = false
        end
        player.TeamColor = BrickColor.new("Medium stone gray")
		frame.Visible = false
	else
		if InmateButtonShake == 0 then
			frame.InmateJoin.BackgroundColor3 = Color3.new(170, 0, 0)
			wait (0.3)
			frame.InmateJoin.BackgroundColor3 = Color3.new(12, 66, 0)
			wait (0.2)
			frame.InmateJoin.BackgroundColor3 = Color3.new(170, 0, 0)
			wait (0.1)
			frame.InmateJoin.BackgroundColor3 = Color3.new(12, 66, 0)
		end
    end
end

local function CivilianJoin()
    if (#getTeamPlayers("Bright orange")) < 10 then
        if player.Neutral then
            player.Neutral = false
        end
        player.TeamColor = BrickColor.new("Bright orange")
		frame.Visible = false
	else
		if CivilianButtonShake == 0 then
			frame.CivilianJoin.BackgroundColor3 = Color3.new(170, 0, 0)
			wait (0.3)
			frame.CivilianJoin.BackgroundColor3 = Color3.new(12, 66, 0)
			wait (0.2)
			frame.CivilianJoin.BackgroundColor3 = Color3.new(170, 0, 0)
			wait (0.1)
			frame.CivilianJoin.BackgroundColor3 = Color3.new(12, 66, 0)
		end
    end
end

frame.GuardJoin.MouseButton1Click:connect(GuardJoin)
frame.InmateJoin.MouseButton1Click:connect(InmateJoin)
frame.CivilianJoin.MouseButton1Click:connect(CivilianJoin)