The Tohoku Shinkansen experienced issues with its coupling system when trains 'Hayabusa' and 'Komachi' had two separation incidents in September 2024 and March 2025. Investigations revealed that the control board, which incorrectly issued signals leading to the separations, failed after approximately six years of service, significantly below the expected lifespan of about twelve years for electronic components. The sudden failure, without any prior indications, led JR East to prioritize installations of enhanced systems to prevent similar accidents in the future.

Upon reviewing the incidents, JR East determined that one case of separation was caused by metal debris affecting the control unit, while further analysis indicated that electrical errors were involved in both occurrences. After replacing the problematic control board in another vehicle, another separation incident occurred, reinforcing JR East's perspective on the electrical malfunction's role in these failures. As a result, the railway company is now bolstering safety features by establishing systems that prevent separations even in the event of incorrect signals being produced by the control unit.

According to insiders, the entire control unit was manufactured in 2013, yet the failed board had been replaced with a new one in July 2018. This rapid failure of the control board within just six years—first failing in February 2024 and then again six months later—has raised significant concerns within JR East and the wider railway industry about the reliability of electronic components used in critical safety systems.