WeldConstraint messes up player movement?

I don't know why but for some reason WeldConstraint screws up the players movement, see for yourself

https://gyazo.com/2c8a0639068b2c76794206186cfca3de

I need some help debugging and figuring out the situation

local weld = Instance.new("WeldConstraint")
weld.Part0 = player.Character.HumanoidRootPart
weld.Part1 = stand.HumanoidRootPart
weld.Parent = stand
weld.Part1.CFrame = player.Character.HumanoidRootPart.CFrame + Vector3.new(2,2,2)