There have been a number of engines falling off the 747 over the years. If the inboard, it has tended to take the outboard with it. Some have led to the loss of the aircraft, others (as here) manage to get away with it.
Notable is that if I am not mistaken it always seems to have happened to freighter aircraft. Yet they make up probably only 5% of the 747 fleet movements. Their max gross weight is obviously the same and many pax 747s go out up to gross anyway. I winder why this problem afflicts freighters.