Reverse light won't work

[grimmerschool2 (PartyNoob)]

Hello. While scripting a light system for like 50+ cars in my game, I ran into a problem with the reverse lights.
Script:

local seat = script.Parent.Parent.Parent:FindFirstChild("VehicleSeat")

seat:GetPropertyChangedSignal("Throttle"):Connect(function()
	if seat.Throttle == -1 then
		script.Parent.Material = Enum.Material.Neon
	elseif seat.Throttle == 0 or seat.Throttle == 1 then
		script.Parent.Material = Enum.Material.SmoothPlastic
	end
end)

Error:

[CodyTheDwagon (cody)]

Would changing :FindFirstChild() to WaitForChild() work?

[grimmerschool2 (PartyNoob)]

I got this warning when changing it to WaitForChild():

[ImperiaI_RBLX (Jimbabwe)]

I replicated your code on an A-Chassis vehicle and adding an extra Parent to the seat variable allowed it to work. Try that.