Freezing Fuel

and the fuel lower in the tank froze and could not be pumped through the system, and when the fuel level got to that point, Bam duel flame out.

They have no solid verifiable theory yet, high probability is that not that the fuel "froze" in the tank but there were sufficient concentration of frozen fuel icicles that fuel pumps failed due to cavitation. And by the way there was no flame out - both engines continued to operate but at reduced level of thrust.