Context: Many studies consider the relation between individual aspects of the software engineering process and bug-introduction, e.g., software testing and code review. These studies typically only identify correlations between their set of variables without accounting for interactions with external variables, such as confounding factors. Objective: Within this study, we provide a broad empirical view on practices of software development and their relation to bug-introducing changes \rev{to enable} future work on causal relations between those aspects. Method: We consider the bugs, the type of change that introduced the bug, aspects of the build process, code review, software tests, and any other discussion related to the bug that we can identify. We use a qualitative approach that first describes variables of the development process and then groups the variables based on their relations. From these groups, we deduce how their (pairwise) interactions affect bug-introducing changes. Results: We found multiple relevant relations within the development process of bug-introducing changes. Logical groups of variables and their relations provide a framework for discovering areas of interest regarding intermediate effects in the process and confounders towards bug-introduction. Conclusion: Software engineering practices applied during the development of bug-introducing changes are interdependent. This work lays the foundation to understand why bugs are introduced using causal modeling, discovery, and inference.