This is the second time I've joined a Festering Core strike and the boss has just... decided not to spawn. There was no Taken orb for it to spawn out of, no enemies in the arena after all three Guardians entered, nothing. Just after I joined (I joined at the beginning of the area, before the Vex portal) another Guardian left, but up until the boss arena everything was fine when I caught up to the player who was still in. A third joined just before we got into the arena, though I'm not sure that had anything to do with the missing enemies. As I said, this was the second time I had joined this strike bereft of enemies. The first, I had joined in the same place, but instead, the entire strike was empty and open up to the empty boss arena. I had joined another Guardian who made it to the boss, so I assume I was in the same position as our third this time, who joined just before we reached the boss. Still, not being able to complete a strike is frustrating. This is the only strike I have ever experienced this in, with every player spawned in and in the same area of the map.