Why can't I add multiple pets to my pet shop GUI?

So in my simulator game I added a pet shop GUI. Everything worked fine until I added a second pet. This is the link to the un-copylocked pet shop (Made by @Azarth) the main script is this:

-- this was for a question on scripting helpers - basic client server logic

local PetStorage = game:GetService('ServerStorage').Pets
local RemoteEvent = game:GetService("ReplicatedStorage").PetGiver
local NotificationModule = require ( script.Notification )
local Pets = {
	['Cube'] = { Pet = PetStorage:WaitForChild("Cube"), Cost = 0 },
	['Slime'] = { Pet = PetStorage:WaitForChild("Slime"), Cost = 1 }
}

local PlayerPets = {}

local function Assign(Player, newPet)
	-- Delete old assigned pet to make way for new pet
	if PlayerPets[Player] then 
		PlayerPets[Player]:Destroy()
	end
	-- Get previous pet name or newPet from Pets
	local Pet = newPet and Pets[newPet].Pet:Clone() or Pets[PlayerPets[Player].Name].Pet:Clone()
	-- Give pet
	Pet.Parent = Player.Character
	-- Assign pet
	PlayerPets[Player] = Pet
	-- SetNetworkOwner erorrs if Parent doesn't exist yet
	repeat wait() until Player.Character
	Pet.PrimaryPart:SetNetworkOwner(Player)
end

RemoteEvent.OnServerEvent:Connect(function(PlayerWhoFired, PetName)
	assert(PetName, 'Provide a PetName')
	assert(typeof(PetName) == 'string', 'PetName has to be a string!')
	local MatchingKey = Pets[PetName]
	-- is the pet even real? Client could have lied
	if Pets[PetName] then 
		local leaderstats = PlayerWhoFired:FindFirstChild("leaderstats")
		local rebirths = leaderstats and leaderstats:FindFirstChild("rebirths")
		-- Are our rebirths actually >= to the requirement? 
		if rebirths then 
			if rebirths.Value >= MatchingKey.Cost then 
				-- They are, assign the new pet.
				Assign(PlayerWhoFired, PetName)
			else
				-- Are not, notify client they lost the battle
				NotificationModule.Message(PlayerWhoFired, ("You don't have enough"):format() )
			end		
		end
	else
		-- Pet isn't real
		NotificationModule.Message(PlayerWhoFired, 'That pet does not exist')
	end
end)

game.Players.PlayerAdded:Connect(function(Player)
	script.leaderstats:Clone().Parent = Player
	Player.CharacterAdded:Connect(function(character)
		-- give them their pet each time they respawn
		if PlayerPets[Player] then
			Assign(Player)
		end
	end)
end)

game.Players.PlayerRemoving:Connect(function(Player)
	-- clean up referance 
	PlayerPets[Player.Name] = nil
end)

But this part is the problem of the scrip is the problem:

local PetStorage = game:GetService('ServerStorage').Pets
local RemoteEvent = game:GetService("ReplicatedStorage").PetGiver
local NotificationModule = require ( script.Notification )
local Pets = {
	['Cube'] = { Pet = PetStorage:WaitForChild("Cube"), Cost = 0 },
	['Slime'] = { Pet = PetStorage:WaitForChild("Slime"), Cost = 1 }
}

If I keep it like this only the slime works.

local PetStorage = game:GetService('ServerStorage').Pets
local RemoteEvent = game:GetService("ReplicatedStorage").PetGiver
local NotificationModule = require ( script.Notification )
local Pets = {
	['Cube'] = { Pet = PetStorage:WaitForChild("Cube"), Cost = 0 }
}

But if I change it to this only the Cube works. Copylocked version of my game