FADEC failure?
pavvyben - I don't think FADEC failure is likely, as there appears to have been a possible common-mode failure affecting the ability of BOTH engines to respond to throttle demands, and the FADECs on the two engines are functionally, electrically and physically independent.
Of course, it may not be a common-mode failure - failures of both FADECs occurring with a short time of each other are not impossible, just very unlikely.
JC