Missed the question back to me, sorry. Mixed cohorts might occur due to the output as user IDs while collection is of usernames - say someone has a repeating events and has a csv output of data for those new users that were retained at a certain activity level from Point A to B and then has new cohort members opt in at Point B but only wants to include those that already survived from Point A and new at Point B cohort members for examining at another Point C. Without the output of usernames to create the active Point B cohort separately this would make the Point C cohort a mix of qualified user ids and new user names. There are several ways of dealing with this, it was just the first scenario I could think of that could cause this. Seems we still need to revisit the possibility of accessing usernames as output, also for reasons of matching to other data points where most users and most program leaders do not know user ids - Jaime