Worked on the cdisc-org/cdisc-rules-engine repository to improve data ingestion reliability for Excel imports, focusing on preserving literal 'NA' string values during data loading. Addressed a bug where 'NA' entries were incorrectly converted to NaN, which could compromise controlled terminology data integrity. Utilized Python and the pandas library to configure data processing so that 'NA' is treated as a literal string, ensuring accurate downstream analytics. Developed comprehensive unit tests to validate this behavior and enhanced continuous integration coverage for Excel ingestion scenarios. The work emphasized robust data engineering practices and careful handling of edge cases in Excel data processing pipelines.