It's easy to listen to your product owner talk about journeys in scrum teams, but if you want to know what's really going on, talk to your friendly customer service adviser.
Who hasn't spent hours agonising over wireframes of new or existing journeys? You trust your UXer to have covered all basis, but that's not always the case. They're human too and might've missed an error or success message. Good customer experience is always about good collaboration.
You'll both benefit by talking to people who talk to your end user on a minute-by-minute basis. They've seen and heard it all, from the extreme cases they regale over a pint down the pub to the heartbreaking ones they pull all the stops out for. They know every nuance of the process and how customers talk about it.
My advice; talk to them, spend the day with them, share their experience on the frontline to build a robust journey written in the customer's language with every eventuality thought through, so the journey is for the many, not the few.
That's when you start winning awards in innovation, customer experience and design.