The fault that had caused the original failure of the tail rotor drive was traced to the fatigue failure of an aluminium alloy spigot incorporated in the yaw control linkage of the tail rotor system, immediately to the rear of the engine bay. Following the fracture of the part the tail rotor became disconnected from the rudder pedals, thereby depriving the pilot of control and depriving the t/r of thrust. The drive to the rotating blade was unaffected, it was just turning ineffectually. In the crash the blades had suffered no obvious damage.
The part involved in the failure had recently been replaced under a Bell modification scheme. In the light of the AAIB findings the manufacturer accepted that the cause lay with their modification and agreed to fund and undertake the complete repair and refurbishment of the 222. Accordingly it was shipped across the Atlantic and rebuilt during 1985 and 1986.
Not quite what it says in the AAIB report but close.