Zana Find Map Mission in Torture Chamber Fails to Complete

Bug Code: 8,789,841

I shared my Zana Level 7 daily mission with 5 others. We found the map (in Torture Chamber) and the mission showed up as completed. After party members left to avoid the boss, they left the party. When I left the map, Zana refused to complete the mission. I was the host of the party and invited everyone myself, and I was in the zone when the map dropped.