NPC Animation not syncing up with item he's holding?

I've made a script where it's supposed to display an NPC swinging a hammer. For some reason, it's not syncing up. EDIT: It works properly in studio, but not in online mode.

(image)

-- Variables --
local hum = script.Parent:WaitForChild("Humanoid")
animation = hum:LoadAnimation(script.Animation)
Balthushammer = script.Parent:WaitForChild("BalthusHammer")
-- Variables --
 
-- Hammer Swing Animation --
while wait(1) do
	if script.Parent ~= nil then
		Balthushammer.Hammer.Sound.TimePosition = 0.4
		Balthushammer.Hammer.Sound.Playing = true
		animation:Play()
	end
end
-- Hammer Swing Animation --

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