Microservices have emerged as a popular architectural paradigm, offering a flexible and scalable approach to software development. However, their distributed nature and diverse technology stacks introduce inherent complexities, surpassing those of monolithic systems. The integration of microservices presents numerous challenges, from communication failures to compatibility issues, compromising system reliability. Understanding faults in these distributed components is crucial for preventing defects, devising test strategies, and implementing robustness testing. Despite the significance of these software systems, existing taxonomies are limited, as they primarily focus on non-functional attributes or lack empirical validation. To address these gaps, this paper proposes an extensive taxonomy of the most common integration-relevant faults observed in large-scale microservice systems in industry. Leveraging insights from a systematic literature review and 10 semi-structured interviews with industry experts, we identify common integration-related faults encountered in real-world microservice projects. Our finaltaxonomy was validated through a survey with an additional set of 16 practitioners, confirming that almost all fault categories (21/23) were experienced by at least 50% of the survey participants.