Industrial software systems are often systems of systems~(SoS) whose full behavior only emerges during operation. They therefore require monitoring techniques to observe systems and detect deviations from their requirements. The focus of existing monitoring approaches, however, is mainly on detecting violations of expected behavior, while support for diagnosing violations is typically limited or even neglected. Diagnosis is particularly challenging in SoS due to their technological heterogeneity and the diversity of development tools in use. Uncovering the root cause of a violation typically requires developers to trace violations to artifacts such as source code or requirements documents, which is difficult without detailed domain knowledge. In this paper we describe our experiences of developing a tool-supported approach facilitating the diagnosis of requirements violations in SoS. We describe how we complemented a requirements monitoring model with a system artifact model relating SoS artifacts needed for diagnosis with monitored events. We customized our approach to an industrial SoS and conducted a scenario-based walkthrough with engineers developing the SoS and engineers and researchers unfamiliar with it. The results of our evaluation have shown that our approach can significantly ease diagnosing violations in a real-world SoS.