There is a bug where if you have more than one UGC mission running and you drop one, it will ask you to rate the next mission up on your list.
So, if I have:
Active, and I drop mission 3, it will ask to review mission 2. Same if I drop mission 2 it will ask to review mission 1. I am not sure if I have aleady rated the mission it adds a new rating to that mission or just over writes my previous rating.
on a separate note, if you take a mission and play it then review it, then take another mission, when you have finished that second mission, what you wrote as the review for the first mission pops up again instead of a blank space.
its not a major problem as you just delete it and put in its place what you want to write but it should really reset itself.