wow, that's a bummer.
I don't have any information, but there are generally enough 77H frames and I don't know of any issues with incoming flights, so I *suspect* it isn't equipment related but rather a pilot / crew issue, and most likely pilot issue. I don't think any frames are out of commission right now.
I suspect pilot because there have been a lot of work-to-rule issues with the pilots for the past 6 months. Perhaps the Captain went sick on your flight tonight? Generally it's easier to sub out FAs than pilots, especially if the Captain is the one with the problem. My understanding is that there isn't a whole lot of slack designed into the pilot rosters, and was designed in such a way that it required pilots not to work to rule. Of course, the pilots argue CX is sweating them to the extent fatigue is becoming an issue. Part of their argument is based on the nature of the routes changing in the last decade, as the 77Ws arrived....as it was described to me, "flexible" was okay getting swapped around on regional flights, but flexible gets exhausting when you're "flexible" 12-16 hour long-hauls at the flip of a hat. Since I've been flying CX pilots always seem to be miffed, while CX mgmt always seems to go out of its way to not give any ground. It's not quite as acrimonious as the US but the pilots always seem to gripe and mgmt never seems to want to lose face by looking weak and giving an inch. It's a lovely dynamic that we all benefit from
I was on a flight a few months ago where our midnight departure took a Captain at the last-minute from the MAN flight, which subsequently went out very delayed.
My *guess* is this is the strongest chance what happened to your flight?