I have a Camera System but after i use it to view exterior it wont let me use it again?

"Script"

local Button = game.Workspace["Camera System"]

local cam = game.workspace.CurrentCamera

function Screen(plr)

if plr.PlayerGui:FindFirstChild("CameraGui") == nil then

local s = script.CameraGui:Clone()

s.Parent = plr.PlayerGui

end

end

script.Parent.ClickDetector.MouseClick:connect(Screen)

"Local script of CameraGui"

local cam = game.workspace.CurrentCamera

local Player = game.Players.LocalPlayer.Character

function CamView()

cam.CameraSubject = game.Workspace.TARDISBeta.Exterior.Parts.View

cam.CameraType = "Track"

end

CamView()

function Cam()

cam.CameraSubject = Player.Humanoid

cam.CameraType = "Custom"

script.Parent:remove()

end

script.Parent.BackButton.MouseButton1Down:connect(Cam)

"LocalScript of Back Button"

local Character = game.Players.LocalPlayer.Character

local Work = script.Parent

while true do

Work.Text = "Back To ["..Character.Name.."]"

wait()

end