Not sure though but I think due to tremendous wastage of Diesel by taking it through the ring railway...the rake now gets shunted from Delhi Sarai Rohilla to New Delhi via Delhi Sadar Bazaar which is actually just 5km..in order to avoid loco reversal issues a SSB WDS6 is being given for shunting purposes while the VATVA ALCO is being parked at New Delhi Trip Shed for the entire day...kindly update if the theory isnt valid lol