Saw a short clip of it...the spectator was hanging out behind a dune, truck crested and went over him...Truck did not stop, I suspect they did not even know they went over him...
Just be sure it is the actuator...mine also did not engage according to the dash light, but it did actually engage the diff lock.
Ie, The switch that was supposed to turn the Diff lock light on the dashboard on and off was faulty...
Please ignore if you have confirmed your problem already :)