I am an ATC and obviously a SLF, not a Pilot.
What exactly is the problem here.
1. I'd rather be delayed (period) than end up swimming the second half of the trip to Perth.
2. The pilot might have known what the symptoms of the failure were, but not the cause so "Technical Problem" covers the Pax on a need to know basis.
3. Some parts of the world and some airlines, anything under 12 hours for a replacement (not fix) aircraft is pretty good.
4. Don't know what/how the passengers were treated (meals-lounge-hotel), but that would (in my opinion) potentially be the only area for complaint in this scenario, but as there is nothing mentioned, I assume that that was all OK.
5. Of course the Pax will be pi$$ed at a 7hr delay, they would not be human if they were not. I would be.
6. Other than a minor comment that implies that the crew did not care, the origional poster was only asking about the cause for the technical delay anyway.
Hey ... Have a nice day OK
Invictus
edited for spelling