I’ve been farming corruptor’s scourgestones to buy old recipes from Old Naxx, been at it about 2 months now. Yesterday after reset Kel’Thuzad bugged out, everything despawned- whatever I did. I’ve done this raid 100s of times in different forms, old and new, never had this before. Nothing on google yet.
mee too today… 
two hours
There are reports that legacy content doesn’t even drop loot if you manager to kill the bosses.
Lemix broke a lot
Unfortunately it’s not the Vanilla version, but Wrath.
ive had Kelthuzad reset for me aswell, i also had a banshee close to the door when i did beat Kelthuzad and floating towards the door, my guess is that when he resets out of nowhere is because a banshee left the room?, ive also seen other mobs move around wierdly in there like patchwerk and grobbulus not walking straight on their path like normal
Someone forgot to oil his bones