I posted with this issue and also commented on someone else’s post about this….now yours. So it seems to only happen when trying to unlock all nodes of the triangle and then going to get the buffs from Lightbearers. My team did this three separate times and soft locked the encounter each and every time without fail. But when we unlocked a node then went to get the buff, one at a time, that worked. So do each node to completion, one at a time. Deepsight to see location of nodes, kill required knight within correct node area, align ring and symbol by sighting down weapon, check symbol, go into caves to find said symbol and kill that Lightbearer thus receiving its Vestige buff. Go grab Deepsight and deposit buff at correct node. Repeat this for the next two nodes. Unleash Hell on boss. Good luck and I hope someone figures out what EXACTLY causes it to softlock as, I personally, would prefer to prep all nodes first and then go grab the buffs (3 nodes, 3 buffs, 3 fireteam members….koinkydink??) as it at least seems to be faster. I haven’t timed it so it might be slower. Lolz