A sensor machine used for detecting railway track occupancy by a train, commissioned by the Railways according to specifications approved by its design and standards unit RDSO, has been red flagged by officials as “faulty” after testing, saying the malfunctioning units could lead to a Balasore-like incident unless withdrawn. Officials said that around 4,000 units of the “faulty” MSDAC system have been procured by the Railways at a cost of Rs 5 lakh per unit and are being tested as part of a trial.