I reiterate
NO ONE KNOWS WHAT THE CAUSE WAS , as I said before any cracking may or may not be a causal factor, nodody knows yet and wild guessing now doesn't help
I believe the aircraft in Italy are still flying, no aircraft are actually grounded (which is in itself a very emotive term) as the Airworthiness certificates have not been withdrawn, they are still available to fly if required.
It is widely overlooked that the aircraft is CAA, RAI and FAA compliant with the requisite rules and therefore any safety case must have been carried out to the certification authorities satisfaction. Obviously it is possible something has been overlooked but the job was done competently enough that all parties were happy, after all the RAF, RN, MMI, CAF, FAA, CAA, RAI and Japanese authorities must have been happy to allow the aircraft to fly. Still nobody is perfect (even Lu must admit to that).
For Crab to say 'But, are Westlands happy to convince the military that they have an airworthy aircraft, despite some high profile failures so that jolly jack tar and the rest of the cannon fodder in the military can play crash test dummies for tthe R & D dept? it would seem so.' is pretty blatant.
for NDT, what about thermal profiles, X rays, ultrasound?