I killed the fell council in tier 7 infernal horde. Immediately after killing the last council member (Geleb the Flame or whatever his name is), one of his already triggered mechanics killed me. I had a revive so I respawned, and when I re-entered the council chamber the chests were in place, but the council members all three respawned and I had to fight them again. I verified that the chests were openable and not just a visual bug.
And for whatever reason, once I beat them again, I could not teleport out of the council chamber. I had to leave the game and log back in before I could get back to Kyovashad.