There is a bug on mission progression at tree of probabilities. (Normal Mission or Assault). The bug block you to progress on the mission, the Ghost is indicating that the objective is behind, but there is nothing to do there ... when you arrive at the boss's room he just doesn't show up. Because of this problem it is impossible to continue the Curse of Osiris campaign. Some attempts I made to correct: 1- restart the mission 2- change character 3- restart the game