Zombie models spawn without arms?

In my game that I am working on I am trying to load zombies from server storage into workspace through scripts, but when it gets loaded in they will spawn with their arms falling off. Is there any way to counter this? I have tried anchoring the zombie then running a weld script for their arms but the arms end up inside the torso giving them a funny wobble.

Weld script:

local zombie = script.Parent
local rightArm = zombie:WaitForChild("Right Arm")
local leftArm = zombie:WaitForChild("Left Arm")
local torso = zombie:WaitForChild("Torso")

function armWeld(arm,name)
    local weld = Instance.new("Motor6D",torso)
    weld.Name = name
    weld.Part0 = torso
    weld.Part1 = arm
end

armWeld(rightArm,"Right Shoulder")
armWeld(leftArm,"Left Shoulder")