Your question is Fixing an Adopted Bad Pipeline. 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).
A pipeline is producing inaccurate data, but downstream teams have already adopted it in reports and operational workflows. You need to stop further spread, assess impact, correct the data, and roll out the fix without causing more disruption.