@anneliese​ In the "Disengaged" tab of any series you can see at which step the user disengaged. Not sure though, if you can access this data outside the series.

Besides what @kevin b​ suggested, you can also export raw data for the series:

And get something like this:

I haven't had a chance to look into this in more detail as it's really raw data and not really self-explanatory what is what (apart from the filenames).

But what I would do instead, is introduce people tags at each "checkpoint" you would like them to pass through. That can help you filter out in Contacts and you can also make some follow-up automated messages for those that might not reach all the checkpoints.

Hope that helps.

Cheers!