AI walking off the earth?

So basically I'm trying to make a simple AI that has priorities

Priorities 1- Light 2- Sound 3- Humans

But for some reason the AI just walks off the earth and ignores them all Here's my script:

local NPC = script.Parent
local Humanoid = NPC:WaitForChild("Humanoid")
local Rootpart = NPC:WaitForChild("HumanoidRootPart")
local DetectionDistance = 50

local GOTO = nil
local Object = nil

UpdateAI = coroutine.create(function()

    while wait(0.025) do

        ------------

        if GOTO == nil then
            GOTO = Rootpart
        end

        ------------

        if Object == nil or GOTO == nil then
            Object = nil
            GOTO = Rootpart
        end

        ------------

        if GOTO and Object then
            local CheckDistance = DetectionDistance

            if Object:IsA("Sound") and Object.Volume >= 5 then
                CheckDistance = DetectionDistance * 2
            end

            if (Rootpart.Position - GOTO.Position).Magnitude > CheckDistance then
                Object = nil
                GOTO = nil
            end
        end

        ------------

        if GOTO then
            Humanoid:Move(GOTO.Position)
        end

        ------------

        for i,e in pairs(workspace:GetDescendants()) do
            ------------------------
            --Lights
            if e:IsA("Light") and e.Parent:IsA("BasePart") and e.Enabled == true then
                if (Rootpart.Position - e.Parent.Position).Magnitude <= DetectionDistance then
                    Object = e
                    GOTO = e.Parent
                end
            --Sounds
            elseif e:IsA("Sound") and e.Parent:IsA("BasePart") and e.Playing == true then
                local CheckDistance = DetectionDistance

                if e.Volume >= 5 then
                    CheckDistance = DetectionDistance * 2
                end

                if (Rootpart.Position - e.Parent.Position).Magnitude <= CheckDistance then
                    if Object:IsA("Light") then
                        return
                    end
                    Object = e
                    GOTO = e.Parent
                end
            --Humans
            elseif e:IsA("Model") and e:FindFirstChild("HumanoidRootPart") and e.PrimaryPart then
                if Object == nil then
                    if (Rootpart.Position - e.PrimaryPart.Position).Magnitude <= DetectionDistance then
                        Object = e
                        GOTO = e.PrimaryPart
                    end
                end
            end
            ------------------------
        end

        ------------

    end

end)

coroutine.resume(UpdateAI)