When Nidhoggur's shadow uses that one skill that teleports players to one of the four corners rooms where they are stuck until the mobs in the room are defeated, the mobs sometimes leave the room. I am not able to leave the room to chase them, however. I suppose it is not an instance-ruining problem as Nid will eventually recast the room teleporting skill. The problem is that it also casts full heal in that time, effectively restarting the fight with fewer supplies. Once in a while, a Ryncho will spawn right at the edge of the status room and make a beeline out the hallway. So cruel!