in normal onslaught some enemies keep instantly teleporting to the ADU and triggering the proximity damage the enemies that always do this are servitors and heavy shanks and their equivalants in other factions sometimes its the exploding units that (omae wa mou shindeiru) my ADU and team back to orbit and yes i know i did not miss them walking by because i see them pop up from thin air i play on console if that is a factor to consider.