This may sound like a trick question, but be honest with your answer. However, be sure to avoid bad mouthing others or admitting to something that is a fundamental basic of project management. Also, focus more on how you fixed the situation versus what went wrong.

"In my previous role, I managed a team with a new employee. My team and I made the mistake of assuming the new employee would know how to seamlessly work around our existing process. After some time, I realized he was slightly confused. I called the team together in order to explain how we work and his specific role on this project. Also, I described how I envisioned each aspect coming together to form a cohesive and successful outcome."