Issue (e.g., defect) repositories usually contain rich information that can be used to mine evidence about team dynamics, issue management processes, and other aspects of software development. The exploratory case study reported in this paper uses quantitative issue tracking data of three open-source projects to derive insights into how issues emerge and are handled in opensource projects. The mined information provides empirical evidence for a few beliefs in the software engineering and process communities. For example, depending on their specific context factors, projects show different degrees of responsiveness to the occurrence of defects. Software engineers can use techniques similar to those presented in this paper to mine the issue repositories of their in-house development projects. This may serve to better characterize their issue management processes, to perform self-assessment and evaluation on them, and also to identify process smells (symptoms) in those processes.