1b) CT boost pumps switch back on uncommanded when pick-ups become covered (is there any way (including failures) that this can happen in the 777 system?).
If this were to produce any effect, the fuel scavenge valves in the wing tanks would have to open or to be open, as an earlier poster said. But at what wing tank fuel level do these valves open? would the amount left in the tanks of this flight come anywhere near that level?
and where are the fuel scavenge line outlets in the wing tanks? is there any chance of ice or slush coming from them partially obstructing the boost pump inlet screens in the wings?