I think WAG-7 poses two issues: Acceleration (geared to pull more load not to accelerate quickly) and 100kmph limit. Contrast this with WAP-7 (which excels in acceleration and has higher top speed). WAP-4 is similar to WAP-7 with better acceleration and top speed than WAG-7. If the train slows down, or is stopped for lack of clearance, WAG-7 will trail and cannot make up with speed either whereas WAP-4 locos will pull at 110+. But more importantly, the train simply doesn't have decent priority, and worse, can't make up for the losses.
NGP-BSP section (411km), for example, has 5:50 for the train with one stop (Raipur, 5 minutes). Gitanjali Express has five stops (Bhandara, 2; Gondia, 2; Rajnandgaon, 2; Durg, 5; Raipur,...
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10), and runs the distance in 6:10. It almost does not get delayed on this stretch despite of these stoppages (easier to make up time without stops than with). OTOH, the ACSF's average delay in this section is 40 minutes. This is happening for all three reasons:
1- Lack of priority (may be even on triple line section, from Durg to Bilaspur)
2- Lack of acceleration from slow downs/unscheduled stoppages (WAG-7 issue, despite of using only 13 coaches or so)
3- Lack of top speed (100 kmph basically limits the train with little to no wiggle room to make up by going 110+, likely only to 80-95).