As I see now, it wasn't a loco problem either because even the 22824 BBS Rajdhani got delayed between Gaya and Koderma by 2.5 hours. Also, each of 12313 and 12301 trains got delayed by 1 hour in this section....So, definitely some kind of problem in the route such as power failure. I think the NDLS-HWh route suffers from maintenance issues...