Infested Invasion Exterminates Don't Spawn Enough

[Godd_Howard]

So, I am currently standing in-game in a Infested Invasion mission trying to get through three runs of this mission so i can get my Fieldrons. Often, more times than not, you will get to the end of the mission with not nearly as many kills as you are required to have to complete it. In this current mission I'm in, the last ten enemies just decide they don't want to show up. I would just like insight on how we still have spawn problems for this mostly PvE dedicated game? How is it that i can reach the end of a mission and have to run back to start from finish at least three times PER mission to finish it, then have the willpower to do it all over again 2 more times? Does any one else run into this? Am I just killing too fast? And the whole time I've taken to write this post, I've kept the mission running and still nothing. Corpus are just standing around me as bewildered as I am. 

[Naftal]

This is true for any exterminates, they've broken them the way they used to be broken some time ago.

Not enough enemies spawn and/or enemies spawn behind you.