The S61N is a great machine to fly. Very stable, just a little short on power. In my distant past I aquired nearly 3000 hours on it and never had an engine problem, except for one occasion when an inlet guide vane problem reduced power on one engine.
Of course the problem with any helicopter is that everything is concentrated up around the rotorhead. If you have a serious fire up there it is going to eventualy effect the oil supply to the gearbox, the engines and the hydraulics. Therefore multiple failures would be expected in this case, given sufficient time for the fire to take hold.