Did Halls of Reflection on Heroic first and after the final fight, escaping from the Lich King, the Loot chest bugged and didn’t open, nor did it have the icon cogwheel for opening. Got a 7h lockout.
After that I did Halls of Reflection on Normal and not only did the loot chest got bugged again, but the Lich King did the Pain and Suffering mechanic from the raid and wiped us all : Pain and Suffering
100 yd range
0.5 sec cast
Deals 7540 to 8460 Shadow damage in a cone effect in front of the caster. In addition, the targets will take 1200 Shadow damage per second for 3 sec.
I checked to see if he can do it in both normal and HC dungeon and he can’t.
I also saw that this has happened many times in the US part: https://us.forums.blizzard.com/en/wow/t/halls-of-reflection-lich-king-loot-chest-not-opening/1687542