I was running survival today and I went to the rooftop extraction point. Called in for the extraction, killed the hunter that spawns for me, but the helo wouldn't land claiming threats in the area. I pulsed and found that there were THREE hunters spawned and down on the street hanging out amongst the corpses of three other people. They were nowhere near the extraction point, but apparently it was not going to let me extract unless I could finish off the three hunters.

Perhaps I was wrong in assuming that once the hunters killed the players, they would despawn as they were part of the extraction event. It doesn't seem to be the case here. I didn't have much time left to try to effectively kill the three hunters even if there was a slim chance of success in 3v1...but it was highly annoying.