This is something else I found a year or so that caused the shell plate to bind or drag when rotating.
I found that where the shell plate bolt seats in the index sprocket, the spocket seat was not perfectly flat where the underside of the shell plate bolt rides.. I took some fine valve lapping compound and coated the sprocket and reinstalled everything loosely. After about 4 minutes of rotating the shellplate and tighting the bolt the tight spot disappeared. Cleaned everything up, relubed and its good to go. No more dragging or plate wobble, Smooth as glass.