RVDT#721 has explained the fenestron fin and structure broke when it hit the air conditioning unit and the ring frame AD did not apply - it had been reinforced. Fair enough.
Nevertheless, the unusual noises heard by several people may have been associated with the tail rotor. (I find it hard to believe this aircraft crashed because the engines stopped.)
A friend of mine died doing aerobatics after a screwdriver was left in the fuselage -- it jammed controls in the tail -- so I can understand engineers getting defensive when something goes wrong.