Now the light is out, try it again for the juddering. If it still does it, reverse slowly and turn full lock each way a couple of times, which should disengage the difflock ... though the light is fairly intimate with the difflock and shouldn't go out if it's still engaged, other forces, 'wind-p' can still be present until they're unwound.

I have to go out later so I will do a couple of full locks forward and back and see if that is the problem that it is still wound up