Microservices have been around for a decade, but operational challenges remain unsolved. The complexity of operating them has been a persistent issue among practitioners, being a barrier to the proper adoption of the Microservices Architecture (MSA) paradigm. In some extreme cases, this situation led to the failure of MSA adoption and a return to monolithic architectures. Throughout a longitudinal exploratory case study conducted at a large financial organization with over 40 years of experience in developing and operating complex distributed systems, we examine the factors influencing the dependability and sustainability at runtime, i.e., the operational stability of microservices. Our findings highlight the need for systematic approaches to define realistic service-level targets, design cohesive and robust stability strategies, and establish optimal resource utilization, thereby framing a research agenda aligned with industry needs. Ultimately, we ensure the quality of our study by adopting a multivocal approach to data collection, employing systematic data triangulation during analysis, and ensuring transferability by relating our findings to previous studies and collecting feedback from non-participants from a different domain.