X30 Stator Mechanical Failure?

I was out racing a few weeks ago and my ignition stopped sparking while going down the straight. Took me a while to diagnose the issue, then I saw the stator rotor magnetised to the bottom of my kart. The rotor supposedly ripped itself out… Has anyone ever had this happen to them? What could be the cause?

The rotor is held on the keyed shaft with a nut, a flat washer, and a spring washer. The nut must not have been tight enough, and the rotor just spun off the crank end.