So I just did AetherBlade Retreat with a group of people from my guild about 5 minutes ago and I forgot that there was a chest at the end of the dungeon so I left the dungeon by clicking on the leave instance tab on the bottom right side of the screen. When my fellow players told me of the chest I went back in to the dungeon but when I got up to the final boss room with Mai before I could even go in the laser shield prevented me from going to the final room so I couldn’t open the chest
It was partly my fault for forgetting about chest but it might happen to more people in the future just FYI.