During July 2025, Ortner focused on enhancing the reliability of the RaGroupby function in the apache/systemds repository. He addressed a runtime error that occurred when processing groups with varying row counts by implementing a matrix padding strategy, ensuring the permutation-matrix could handle heterogeneous group structures without exceptions. Ortner supplemented this fix with targeted tests to validate correctness and prevent future regressions. His work, utilizing Java and DML with an emphasis on algorithm implementation and data engineering, improved the robustness of data processing for diverse datasets. The depth of his contribution lies in both the technical solution and comprehensive test coverage.