Studio crashes when a round loads?

I know the title may be vague, but there wasn't really any better way to explain it. Basically, I'm making a game that works in a round system (ROBLOX version of Trouble in Terrorist Town, if that helps). That is, pre-game, in-game, post-game, repeat.

But I noticed an issue. I made a server with four players in Studio and it crashes when the round ends, after a certain message.

Here's the snippet of code the error should be around:

local mapDir = game.ServerStorage.Maps

    local newMap = mapDir:GetChildren()[math.random(#mapDir:GetChildren())]

    local m = Instance.new("Message",game.Workspace)
    m.Text = "New game starting with the "..newMap.Name.." map..."

    wait(5)
    m:Destroy()

    newMap:clone().Parent = game.Workspace.Map

    local newTraitors = choose_traitors(2)

    for a,b in pairs(playerDir:GetChildren()) do
        local val = Instance.new("IntValue",b)
        val.Name = "traitor"
        for c,d in pairs(newTraitors) do
            if b == d then
                val.Value = 1
                break
            end
        end
    end

    for a,b in pairs(playerDir:GetChildren()) do
        if b:findFirstChild("dead") then
            b:findFirstChild("dead").Value = 0
        end
    end

    in_game = true
    script.in_game.Value = 1

end

The script crashes the pseudo-server after the m.Text = "New game starting with the "..newMap.Name.." map..." message displays for 5 seconds.

(if you need the choose_traitors() function, ask)