Can someone explain or point out why this script crashes Roblox? [Sorry, it was just a silly error]

This script was literally working yesterday. Now every time the Player jumps off the seat it freezes and crashes Roblox. I get no errors, parenting is correct. There's no reason it should be acting like this.

seat = script.Parent
function onSitUp(child, Drift, EMP, GUI)
    if child.Parent == nil then
        Drift.Disabled = true
        EMP.Disabled = true
        Drift.Parent = script
        EMP.Parent = script
        GUI.Parent = script
    end
end

function onChildAdded(part)
            local char = script.Parent.Parent.Parent.Parent
            if char then
                local Drift = script["Drift"]
                local EMP = script["EMPscript"]
                Drift.Parent = char
                Drift.Disabled = false
                EMP.Parent = char
                EMP.Disabled = false
                local GUI = script["Controls"]
                local player = game.Players:GetPlayerFromCharacter(char)
                GUI.Parent = player.PlayerGui
                part.AncestryChanged:connect(function(child) onSitUp(child, EMP, GUI, Drift, script.Parent) end) 
            end
end

seat.ChildAdded:connect(onChildAdded)