Quote from Concours77:
"This should rebut any discussion of paralyzing fear, the flee fight syndrome, or other theories indulged to establish abnormal reaction/behaviour?"
It might at first seem to rule out the startle factor, but I can assure you that the sudden, unwanted sound of the "cavalry charge" (audio signal of AP disconnect) is not conducive to relaxation on a dark night. Add to that some turbulence, a partial loss of primary flight-instrumentation, and ECAM warnings, and none of these physiological/psychological factors can be ruled out.
The sidestick needed to be used with the utmost care, as others confirm above. Fear, or even tension, make that more difficult. The muscles of the forearm and hand may tighten, which could well have caused the PF to pull on the sidestick unintentionally (see my previous post), particularly if he was preoccupied with trying to keep the wings level in unfamiliar, roll-direct law.
Another possible difficulty controlling the sidestick would have arisen if the PF' s seat was too far back, or if his sidestick armrest was not deployed correctly.
The bottom line is that this crew lost situational awareness, or they would never have allowed the aircraft to climb 2000 feet without specific comment. That alone suggests mental processes associated with fear and/or overload. During that climb, they were not sitting there drinking coffee or reading a magazine.