When my 11 gearbox had it's M94 bearing probs and was fixed y Steve Scriminger he said that the trouble with this problem is that if the bearings went really bad it would lock the box and so the rear wheel. Obviously the clutch would not unlock this.
The input spline wear probs seemed to be 1150 specific but I guess that a gearbox out and inspection is the only answer.
Good luck...