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