I love them too, they're quite the novelty.
I've had one in hand many years ago.
I was running it back and forth on I think drill rod or really clean SS rod, it would jitter.
I kept trying to adjust it but gave up.
You need a harden and ground steel rod.
You want to also make sure that there are no burrs or nicks on the perimeter of the bearing, discard the bearing if you find any thing wrong with it.
It's possible that your housing has also deflected due to creep (stretched).
So you might need to implement a maintenance routine.