Cetus/Narmer Bounty bonuses not applying

[(PSN)b5riang]

So I was recently doing the Narmer bounties on Cetus with a friend doing the "Rise and Fall" with the assassination at the end. We killed all enemies required in under a minute and it was not marked as complete. Even completing this phase of the bounty, it was not counting as completing the bonus objective and did not give us the extra reward at the end. Has anyone else had this issue? Because it's been reoccurring every time we play it.