dear PinB,
I am one of your 777 Flight Crew and as such used to believe that it might be an EEC software error however the NEW AAIB report clearly narrows the possible cause down to one specific area.
Software errors always happen, on any plane so it would have been plausible.
The AAIB wouldn't have written this report without proving that another error would have been a better fit for what has happened.
Fact of the matter is we don't know how ice behaves at high altitude at extreme low temperatus in a complex mix of JetA1.
Certainly in my mind we can put the software glitch to bed.