Normal.
Nothing. Thats’s TAA.
You can makenit a little better by outputting WPO velocities in the base pass and setting up to spend rendering MS on fixing the ghosting a bit, but it’s not a cure all or much better in practice…
People generally disable motion blur if they can. The engine does some pretty bad motion bluring. Doesnt mean you should disable it, just dont rely on it for a clean render…