When I read the Accident Update (27th May) two things jump out at me.
At around 2 h 11 min 40, the Captain re-entered the cockpit. During the following seconds, all of the recorded speeds became invalid and the stall warning stopped.
At 2 h 12 min 02, the PF said "I don’t have any more indications", and the PNF said "we have no valid indications". At that moment, the thrust levers were in the IDLE detent and the engines’ N1’s were at 55%. Around fifteen seconds later, the PF made pitch-down inputs. In the following moments, the angle of attack decreased, the speeds became valid again and the stall warning sounded again.
So the system is such that entering extremely high angle of attack invalidates the speeds, which in turn silences the stall warnings. Conversely, reducing the angle of attack causes the stall warning to reactivate. The crew are in a situation where they are getting the exact wrong feedback. Couple this with possible mind-sets about turbulence, overspeed and structural damage – just my thoughts.