Anyway, to stay with the subject, and as indirectly suggested by the Airbus OIT, it seems logical to suspect that both FMU's found something in the fuel they didn't like. Is there any mechanical part in those units that could have totally seized after 4 hours of this flight ?
It's near universal to protect the controlling innards of the FMU from fuel contamination by virtue of filters relying on fail-safe (at last commanded power) should things go south.
I'm anxious to follow the factual releases on this incident from RR and Airbus.