I have all missions, side missions, encounters and all intel except for echo rogue agent 6 which seems to be bugged for my character. There is a gate covering the door that lets you into the building to complete that echo. After doing a challenge with a group I noticed a new side mission and it was exactly where that echo is. While finally entering the building the leader of the group disbanded the group... So I figured out that if someone who has completed that echo would let me join their group and finish the echo it would be much appreciated.
GT FinneyTheFreak
on Xbox One