Describe a specific situation where a model you deployed to production unexpectedly underperformed. How did you detect it, diagnose the root cause, and fix it?

Interview question asked to Data Scientists interviewing at Huawei, Verizon, Canva and other companies. Original question asked: Describe a specific situation where a model you deployed to production unexpectedly underperformed. How did you detect it, diagnose the root cause, and fix it?.