Abyss breaking when next to other content

Most the time when I've encountered Abyss in maps it works fine. However, when there is other content near it (Strongboxes and Breaches especially), it refuses to spawn the final mobs in order to activate that abyss for rewards. I've hunted every pixel next to the breach for something to spawn the last mob I need to kill to activate it, but no luck. It just breaks.