So here's what I THINK COULD have happened: The a/c was rolling at taxi speed toward the turn pad at the end of the runway, when suddenly there was a technical malfunction (NWS, left brake suddenly fully blocked…) causing the a/c to veer to the left. And just before it stopped it rolled over the edge.
Happened before. Nose gear deflection on landing roll which initially can be compensated by rudder but not at low speed.
nosegear malfunction due to birdstrike