[511,228,274] Locked out of boss area in Grimhaven map.

There is a breach in this map that expand into the boss area.
Upon clearing the map and come back for boss the area appear to be blocked by red mist, audio of boss spawning can be heard from the other side.
Portal back and reenter does not solve the issue.
P/S: I may have passed the location of the red mist while doing the breach from earlier, but was backing out as soon as I see the red skull on minimap.