One probable reason.
Mgs ald section is cleared of freights for Rajdhani gang to whip past as soon as 12301 is about to leave mgs . once all the hurricanes passes all the freights stopped starts moving towards ald slowly. 12817 leaves mgs just after this gang and it get mixed up with this freight due to huge bottlenecks and congestion which were stopped previously. Tracks get oversaturated.