Ark Royal,
It was OC RAF Odiham who first concluded that there had been a failure in the duty of care. The AOC and C in C agreed and concluded the failure amounted to Gross Negligence.
As they told the HOL Committee, negligence occurred at or before the waypoint change by which time the pilots had failed in their duty of care and airmanship by not having taken action to avoid the cloud covered cliff that they must have known was ahead.
Even if there was a subsequent transient and undiscovered technical failure that does not mean that the pilots negligence ceases to be a contributory cause of the crash. They had to be in no doubt whatsoever that negligence was a cause (not necessarily the sole cause) of the crash.