"Good results can hide a bad condition."
— The Generalist’s Advantage
One of your most valuable people may be quietly fixing the same problem every week. Because the work still gets done, nobody puts the underlying condition on the priority list.
Before you praise the result, ask what had to be repaired to produce it. If the same person keeps supplying missing context, resolving the same conflict, or catching the same error, treat that repetition as evidence.