This article discusses a case study in which 14 advanced undergraduate physics students taking an honor-level quantum mechanics course were given the same four problems on midterm and final exams. The solutions to the midterm problems were provided to students. Their performance on the final exam shows that although some advanced students performed equally well or improved compared to their performance on the midterm exam on the problems given twice, a comparable number performed less well on the final than on the midterm exam. The wide distribution of students' performance on problems given again suggests that most advanced students do not automatically use their mistakes as an opportunity for learning, repairing, extending, and organizing their knowledge structure. Interviews with a subset of the students revealed attitudes toward problem solving and gave insight into their approach to learning.