When you first go outside, the enemies down the hill you are supposed to go do not spawn. The only enemies you encounter are the first two squads of Sentinels and the first two squads of Covenant. But if you restart the mission, the enemies spawns.
What’s going on here?
this is a normal glitch, it happens when you do something with the door leading outside, although I forgot what, this can actually be useful for getting the look out for the little guys achievement. I’m almost sure if you restart the level and open the door normally it won’t happen again