Lord Kazzak keep fading out with entire raid....?

Trying to do the seasonal daily to kill Kaz… but every time I get close the guy and the entire raid phases out…

I have tried warmode on / off
I have tried talking to that girl that swaps the zone before joinging riad, while joined the raid and in both phases.

any ideas?

edit : Met a bunch of locks with same problem… if you stand on the hill at the entrance and the tank tanks the guy closer (near the grass) you can send your pet in and get credit.