Expedition AOE bug

I have died on a few occasions while fighting monsters in expediton to a large detonation. I recorded my last death and upon playing the footage back there is literally no visual cue. it looks as if there should be a circle appear to warn you but there is none. I went back to the encounter only for the enemy to kill me again even while off screen. This is incredibly frustrating being blown up by an AOE you cannot see.