Ok lets wait for the ATSB report!
No black boxes, video evidence is out clearly showing prior flight and crash.
ATSB when no video, obtains its evidence from Joe Public and remains of aircraft if any and aircraft pilot records when no boxes.
ATSB are not 100% correct and it is only often a opinion of a possible cause - for this in almost any crash we wait 1 year.
For this alone ATSB lose much credibility, but funniest of all is Pro Pilots will then place comment on said ATSB reports (after the experts will all information and data have concluded the report) these said pilots have largest watches of all.
The Mallard stalled, no report of engine inconsistencies ("Pilots" on here witnessed the crash) sadly Pilot error claimed his life and his girlfriend. It was not his intention but he caused the accident to happen.
My condolences to family/s in particular his and her kids.