Worked on the pkp/omp repository to enhance the reliability of HTML monograph downloads by addressing a critical backend issue in PHP. Focused on refining the download workflow, the developer implemented a targeted fix in the HtmlMonographFilePlugin to prevent a TypeError and eliminate duplicate downloads when no chapter is assigned. This was achieved by introducing a null check for chapterId before invoking ChapterDAO::getChapter(), ensuring the download callback aligns with existing patterns in CatalogBookHandler. The work improved code maintainability and reduced user-facing errors, demonstrating careful attention to edge-case handling and adherence to established backend development practices in PHP.