As more information comes out, to me it seems more like a mx issue. Apparently there were two Airworthiness Directives recently issued for the 777 fleet. One had to do with internal wires in the **** crew 02 masks, which could (and did) start a fire, in the oxygen hose!

The other AD was about cracking in the fuselage skin around the SAT COM antennae mounting area, which, if not repaired, could cause a rapid decompression.

Either one of these two issues, especially the 02 hose fire in the ****, could have caused them to divert and descend, then go unconscious.