For whatever reason, I felt the rope going through the my hand and thought (in that split second sort of way) that the grigri was failing, at the moment of the fall my right (break) hand was at the bottom of the rope about to take up slack so it was only about 3 or 4 inches away from the grigri.

... I desperately squeezed the rope in my hand and basically, kept just enough tension on the rope so that the grigri would not lock, but since the hand was so close to the grigri I could not create enough angular force to make the rope lock in the traditional, non-grigri way.

...After the incident it became apparent that a) the grigri was fine, b) my holding on the rope like I did was the cause of the entire issue.