speedometer bounces?

I had that in 2 cars (65 Newport, 82 Aries). Not the cable, the spinning magnet was wobbling. In the Newport, it grabbed the cup, twisted it and (thankfully) broke the cable, under prior owner so no speedo when I bought it (1991). I sent the spinning magnet part to a speedo shop in Bakersfield and they sent it back re-bushed in bronze. Very steady needle since. The Aries was cheaper w/ the magnet in a plastic press on snout that cracked. I wrapped thread tight and coated w/ epoxy to get a tight fit and worked great until I junked the K.