Lost City of Amdapor

Time: 1:38 GMT+3
Frequency: once
World name: Excalibur
Character name: Kababa
NPC name: none
Monster name: Arioch
Class/Level: 50
Party or solo: Party
In-game time: 4:31PM
Area and coordinates: Lost City of Amdapor X10 Y12
Steps:
The boss supposed to fly when no one has the debuff from killing the adds
he flied twice when the tank lost the debuff twice without getting them back in time
but when the tank lost the buff for the 3rd time the boss didn't fly was around 40%~
boss hp , the boss just stood still and stopped attacking the whole fight till he died , the tank even moved away from the boss but the boss didn't follow , just stopped . was a free kill D:

Confirm same here. The boss's AI breaks after its HP lowers to around 40%.

I have seen this as well. Actually on my very first run in the zone. A second time this past Sunday.

I have seen this as well but noticed everytime it happens when the tank go off killing all the adds & have 5 or more stacks on them. (since its a stack that increases damage & you really only need 1 or 2 on you)