So tonight a group of people and myself ran the Leviathan.. We got to Callus, and after a few wipes, we finally got him down. In the last part of the fight, where you're burning through his shield, we killed him at the very last moment before he finished casting his ability and wiped us. He exploded, we wiped, and it gave us the Invitation as if we had killed him. We weren't able to revive, or do anything at this point. We had someone in our fireteam reconnect and see if he could revive us so we could get our loot. When he rejoined, he just kept dying after walking a few feet. Eventually, we gave up and went to the tower, where our loot was waiting in the postmaster.. However, the milestone for completing the raid and "Defying the Cabal Emperor" was not complete, therefore I did not get my luminous engram. I've only seen one other post for this, which I linked, and was wondering if there was any way to correct this so I can complete that milestone for this week. TL;DR: Killed Callus and wiped at the same time, instance bugged out, didn't complete our milestone, but did get loot.