It's all about the priority terms! NCR gives priority to Rajdhani obviously following Pushpak, TN, Goa, GT, Telagana, While NR gives priority to trains which are bound to nizamuddin because trains bound to NDLS has halt at NZM for 2 minutes and platforms are only 2 because of which trains gets delayed.
Less number of platforms and more trains is also an issue. Jhansi has 2 pf for UP, Gwl has 1, Agc has 2 and MTJ as 1/2. this also decide the the priority.
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more... NCR(jhansi, agra) is known to run trains on mutual delay not like NCR(Ald) which keeps on delaying the train once it gets delayed. For example Train on ALD gets delay by 30 mins it will be delayed at CNB by 2 hours and NDLS by 4-6 hours
On other hand NCR(JhS/Agc) If train enters jhansi with delay of 30 minutes their only might be difference of few minutes here and there exception are obvious.