Welding script that welds a model to a chassis makes the parts from the model at the wrong position?

i made a weld script, that welds the body to the chassis. When im not playing the game (not playing) it looks fine. But if i play the game, some parts are at the wrong place. Whats wrong with it?

not running:

https://cdn.discordapp.com/attachments/438417429564227585/503561157240553502/ unknown.png (remove all the spaces)

when running:

https://cdn.discordapp.com/attachments/438417429564227585/503561565983735823/ unknown.png (remove all the spaces)

script:

local parts = script.Parent:GetChildren()

for i = 1, #parts do
	if parts[i]:IsA("BasePart") then
		local w = Instance.new("Weld")
		w.Part0 = script.Parent.Parent.VehicleSeat
		w.Part1 = parts[i]
		w.C0 = script.Parent.Parent.VehicleSeat.CFrame:Inverse()
		w.C1 = parts[i].CFrame:inverse()
		w.Parent = script.Parent.Parent.VehicleSeat
	end 
end

thank you!

function Weld(x,y)
	local W = Instance.new("Weld")
	W.Part0 = x
	W.Part1 = y
	local CJ = CFrame.new(x.Position)
	local C0 = x.CFrame:inverse()*CJ
	local C1 = y.CFrame:inverse()*CJ
	W.C0 = C0
	W.C1 = C1
	W.Parent = x
end

function Get(A)
	if A:IsA("BasePart") then
		Weld(script.Parent.Handle, A)
		A.Anchored = false
	else
		local C = A:GetChildren()
		for i=1, #C do
		Get(C[i])
		end
	end
end

I am using that weld code whenever I want to weld something. You just simply Get(script.Parent).