Uplinker:
I still wonder if they had a compass/heading malfunction, because I find it hard to believe that a longhaul B777 crew would ignore such basic instructions otherwise.
The 777 doesn't have a compass. It is a highly redundant inertial system (three inertial platforms) that also has mag var tables to convert true heading into magnetic heading when in domestic airspace. These inertial platforms also provide the attitude platform for the airplane. On rare occasions one inertial reference unit (IRU) might fail. In that rare event the airplane only loses triple redundancy.