Without giving too much away story wise, I encountered a bug of some kind with the final mission boss. When reaching the final "stage" we *should* have been greeted with a rally banner location and a darkness zone. None was present (it was in the previous encounter). The boss spawned, but NO additional enemies, and the boss was undamagable (yes I know how the encounter works - doing the prescribed method of DPS boss was still immune). Went to orbit, reloaded game, everything. Nothing would correct issue. Both people in my party loaded the checkpoint separately and both were still glitched. Eventually joined an LFG for someone at same checkpoint whose checkpoint was not glitched and completed fine. One of us was on Steam, one of us was on Xbox so I don't think it to be a platform specific thing.