Report out. It took the ATSB almost a year to come out with this.
What the ATSB found
The ATSB found that the pilot was likely experiencing a level of fatigue due to inadequate sleep the night before and leading up to the incident. Further, operating at 11,000 ft with intermittent use of supplemental oxygen likely resulted in the pilot experiencing mild hypoxia. This likely exacerbated the pilot’s existing fatigue and contributed to the pilot falling asleep.
Full report here
https://www.atsb.gov.au/media/577971...-032-final.pdf