Enemies not spawning properly

[(PSN)OriginalEquinox]

So i just finished a Axi mobile defence fissure without opening my or my teammates relics because throughout the mission only around 40 enemies spawned and dropped 5 reactant, after that they stopped spawning entirely, we went around looking thinking they might be stuck somewhere behind a wall or something (it happens a lot on Neptune defence forcing us to go looking for them) but found nothing, I've experienced this a couple times before as well so it can't be a isolated incident, hope you can look into it, thanks.