At the first boss encounter, where the step says “Pursue Lilith and Vhenard with Neyrelle”, it took me past the ancient gate and won’t let me come back to the boss encounter. I was able to run through the rest of the enemies until you can’t go any further, but I can’t go back through the Ancient gate as it says “The door is sealed”.
I’ve attempted teleporting out and into the dungeon, and I have also teleported out and ran back through the dungeon to the spot again. Once I get to the encounter it teleports me to the other side of the ancient gate again and says “Can’t join boss encounter”, until this returns back to the normal “The door is sealed” message again.