Here's some of the clear evidence James was talking about showing that Vader's blade doesn't spin. Follow the ding in these consecutive frames!
Now follow the bump and see the blade colors switch.
Bump is now on a blue blade:
Blade spinning artifact on red Obi-Wan blade:
Now follow the bump and see the blade colors switch.
Bump is now on a blue blade:
Blade spinning artifact on red Obi-Wan blade: