The issue involving uncommanded altitude deviations was first addressed in 2021.
The Airbus A350 crews were then been given a revised altitude-selection procedure as investigations found that a failure of the altitude selector dial located on the flight control unit resulted in changes to the target altitude with the European Union Aviation Safety Agency (EASA) releasing a directive in November 2021.
However further investigations revealed that the fault lay in the manufacturing process of the ALT knob encoder.
A new proposed airworthiness directive will be closed for consultation on 7th December to be issued data later time.
According to SimpleFlying the proposed AD will mandate the amendment of the AFM at different timelines. For Group 1 aircraft, whose FCU was not listed as an affected part, operators had to incorporate the AFM TR within three months of 02nd December 2021. Group 2 aircraft, which do not have the affected FCU, the AFM TR has to be included in the manual within three months after the effective date of the new directive, which is yet to be determined.