This gearbox was one of three critical technologies on the helicopter that had not reached the desired levels of maturity by the time system development was launched in late 2005. Problems still had not been fully resolved in 2014 when a redesign of the MGB delayed the aircraft's maiden flight, which was finally achieved in October 2015. The US Office of the Director, Operational Test and Evaluation (DOT&E) 2018 report released earlier this year noted the MGB's low reliability and reduced service-life projections.
Low reliability and reduced service life projections are not supply chain issues. The above indicates a problem with the basic design which has not been solved in 14 years.