I know there have been similar fixes, but this seems like a slightly different cause. As an invader, I died during an invasion and my piker mortar got the 6th kill right as I respawned. Instead of being pulled to the reward room, I was left in the instance with the other players. Misadventuring myself respawned me in the reward room correctly. If the specific invasion instance is helpful, it's the only one that I ran today.