Why UXer within an Agile team?

A UXer can act as a SME during a sprint planning meeting or be a resource during a research task. The UXer can impart their knowledge of the user groups on the devs and designers so they're better armed to make decisions while building. An example would be helping the dev/design team understand a user's workflow. This way unnecessary 'things' don't get in the way during the build.

The can also be valuable if there is a research task or tasks that involve user behavior. In my experience, a UX helps with story building and is a great resource. If there isn't a designated UX on a team, then product marketing or product management will be that resource.

As far as troubles, a UX may get pushback about process. For example a dev may want to build a process a certain way b/c it's easier, but if it doesn't fit w/ the desired user experience like too many clicks, incomplete task etc... then the UX would need to step in. However, in my experience the UX works closely w/ dev from the start so friction isn't any more than normal.

Overall, the UX is there to help the dev/designers and the whole company understand their user groups and ensure their experience isn't compromised. UXs' meet with users, observe how they use the product and architect the experience throughout. Usually they have a good grasp on design and conventions and can help interpret user data into actionable tasks. In some cases they'll wireframe a use case or scenario to help the team see clearly.