Why is my :Lerp for placement preview spazzing out?

I have this script that's meant to move a preview for placing something, and I tried to make it lerp when you move the preview (similar to miner's haven), but for some reason it instantly starts spazzing out, am I doing something wrong here?

MMC = mouse.Move:Connect(function()
        local x = clamp(mouse.Hit.p.X,GridMin.X,GridMax.X)
        local y = clamp(mouse.Hit.p.Y+Preview.Hitbox.Size.Y/2,GridMin.Y,64)
        local z = clamp(mouse.Hit.p.Z,GridMin.Z,GridMax.Z)

        if OldPos ~= Vector3.new(x,y,z) then
            spawn(function()
                local LerpStart = OldPos
                --Preview:SetPrimaryPartCFrame(CFrame.new(snapTo(Vector3.new(x,y,z),Grid)))

                for i=1,60 do
                    Preview:SetPrimaryPartCFrame(CFrame.new(LerpStart:Lerp(Vector3.new(x,y,z),i/60)))
                    wait(0.01)
                end
            end)
        end

        OldPos = Vector3.new(x,y,z)
    end)