Those heretics can be a sneaky bunch! You managed to find them all in the end, though, right?
This is a bug. We could not complete the mission for several minutes, then we were randomly able to finish, we did not do anything to make this happen.
That’s interesting; and you’re sure no teammates found the enemies while you were waiting? I’ve asked some developers if there’s anything that might have caused the objective to finish on its own after a time, and will get back with you if I get confirmation. Please bear in mind that we can only act on what information you’ve given us (cannot complete), and sometimes what we can correlate on the backend (mission completed).
No official word yet on what might cause the objective to end like that, but we did find another report of this happening at the end of this mission. A player said that the objective cleared immediately after one person in their group left the game, although that could have been a coincidence. Did anyone in your group leave after your objective got stuck, but before you finished the mission?