"...achieving one “stability event” every 15 hours. "
Umm, to a mere mortal like yours truly, I read this as being that it managed to be stable once every 15 hours.
Shirley this might be better termed an 'instability event'? However, reading the test results to date, it might really be that it manages to get airborne once every 15 hours.
Tell me again why Australia is participating in this farce? With the capability so far demonstrated, even our trans-Tasman cousins could overfly us with impunity with a flight of Plastic Parrots (CT/4 Airtrainers).