Having an issue with some the parts of a model not being welded onto the player's body correctly?

Demonstration of the issue: /a/gBwqP (imgur) The bottom image is what it's supposed to look like, the top image is the bug itself.

for i=1,#A do
			if A[i]:IsA("BasePart") then
				local weld1 = Instance.new("Weld")
				weld1.Part0 = chest
				weld1.Part1 = A[i]
				local ab = CFrame.new(chest.Position+Vector3.new(0, 0, 0))
				local C0 = chest.CFrame:inverse()*ab
				local C1 = A[i].CFrame:inverse()*ab
				weld1.C0 = C0
				weld1.C1 = C1
				weld1.Parent = chest
				local weld1a = Instance.new("Weld")
				weld1a.Part0 = plrChest
				weld1a.Part1 = chest
				local abc = CFrame.new(plrChest.Position+Vector3.new(0, 0, 0))
				local C0 = plrChest.CFrame:inverse()*abc
				local C1 = chest.CFrame:inverse()*abc
				weld1a.Parent = plrChest
				A[i].Anchored = false
				A[i].CanCollide = false
			end
		end