Investigating error in healthcare has long been a central focus of patient safety efforts, yet this approach oversimplifies the complexities of a deeply interconnected and dynamic system. This paper argues that framing patient harm solely as "error" has failed to yield meaningful improvements, as it overlooks the broader factors contributing to adverse outcomes. Through a case study, we illustrate how an exclusive focus on error investigation missed critical insights and propose that attention should instead be directed towards identifying and managing hazards. Emphasizing the importance of treating healthcare as a sociotechnical system, we argue for the application of sociotechnical system thinking, particularly in addressing diagnostic errors in high-pressure environments like emergency medicine. The traditional methods, such as root cause analysis, error investigation, and the Swiss cheese model, are no longer sufficient. These outdated frameworks fail to address the systemic challenges clinicians face and often misguide safety interventions. The paper calls for a paradigm shift towards re-designing healthcare systems using human factors research to better align with the complexities of clinical work and the hazards that lead to harm.