Was playing on Airship and fighting the first boss near one of the masts.
After dodging the AoEs, the boss suddenly disappeared from view, but the boss was still able to attack the party. We found the boss on top of one of the masts where the tank was unable to hit it (and provoke seemed to be ineffective). The boss did eventually walk down as if coming down a ramp when it went after a dps near the exit portal.