The article systematizes and analyzes five typical system errors that occur when deploying complex security systems at critical and industrial infrastructure facilities. Based on the analysis of current scientific publications and generalization of practical experience, including the case of the El Dabaa NPP construction from Pavel Mishchenko, the study identifies weaknesses in modern approaches to design and installation. The purpose of the work is to provide engineers and project managers with a scientific and practical basis for minimizing risks and increasing the overall reliability of security systems. The article discusses errors associated with the lack of system integration, ignoring the physical level of infrastructure, underestimating the human factor, false economic optimization, and lack of planning for the full life cycle of the system. The results of the study can be applied to the development of project management methodologies in the field of industrial safety, as well as to improve the skills of technical personnel.