i kind of remember something from there. there's comment on that video by Reza Mirzaei:
Intel 4 does not spawn if you take the elevator as shown here. Once you've interrogated the first officer (in the barracks, intel #6), go back out and take the top entrance/elevator in the court yard. That is the first open area with enemies you come to (two sniper towers on each side with security cameras). There are two ways further from there: one to the barracks and one (the top one) to the gallery.
maybe that's your problem.