Investigate a Difficult Problem in Depth

Describe a difficult problem that required deep investigation and analysis. ### Constraints & Assumptions Use a real example and distinguish your contribution from the team's work. The source provides the interview question, not a candidate answer; illustrative stories in the solution are fictional. ### Clarifying Questions What made the problem difficult to explain? What evidence did you collect? Which hypotheses did you reject? What did you personally discover? ### What a Strong Answer Covers A specific symptom, a disciplined investigation, evidence that distinguishes causes, a verified fix or conclusion, and prevention or learning. ### Follow-up Questions What was your first incorrect hypothesis? How did you avoid confusing correlation with cause? How did you verify that the underlying problem was resolved?