On 9 November 2018, a Lilydale-bound service, led by 959M, uncoupled in running shortly after departing Croydon Station, splitting into two 3-car units, with the trailing unit coming to a stop under emergency braking. The subsequent investigation found that a wiring error during a modification to the train's low-note whistle on 959M, combined with a deterioration of insulation resistance in the uncouple solenoid connector of 882M (the leading car of the trailing unit), resulted in an error circuit forming which resulted in the unintended coupling.