Your question is Diagnose Source vs Pipeline Issues. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
You are supporting a customer-facing data pipeline and need to determine why the data in the destination looks wrong. The issue could come from the source system, or it could be introduced during ingestion, transformation, or loading.
How would you investigate whether a customer's data issue is caused by bad source data or a platform problem?