For return train timings clash with Gomti at Cnb. 12988 would also not reach before 3 am at Mgs. Guaranteed. It has been put into a busy slot, as 12424 would ot it before Ald. And after that it will easily come in radar of Rajdhanis.
Also 12987 will be disturbed by Gomti after Cnb, even if dep 5 mins late