I just finished Prison of Elders for my second time on level 35. I finished it on my warlock last night as a level 33. I have 3 other characters, but now my warlock is a level 34. So naturally, I decided it would be easier to use my warlock to run again and then I would switch to my level 33 Titan at the end to get the rewards. Good idea right? Wrong. There is an error saying "unable to join fire team because their activity is almost finished. Try again soon!" So I just wasted 2 more hours of my day... Thanks Bungie.