Received the message Joining Encounter in Progress at the start of the battle, while alone and not in a group. While fighting Nathari, at the point she uses a portal to slip away and Arana tries to contain the darkness, she never reappears but her damaging aoe follows me endlessly. There are two copies of Arana: one at the portal, another granting protection but no Nathari. Her health is stuck at halfway. Unable to exit the arena, choosing reset to wayshrine simply restarts an unwinnable battle. A force quit and restart stuck me at the beginning of the barrow so I had to refight all enemies to reach her only to have the problem repeat. I've lost soul gems, and quite frankly, patience. Not to mention the achievement Red Eagle's Flight is also bugged. Jumped three times and got nothing. Both this quest and the achievement were obtained by another character without issue only yesterday, so I am familiar with the mechanics of both.