I need a sharp backend troubleshooter to stabilise an existing API. The core problem is incorrect data mapping that surfaces in our data-retrieval endpoints, leading to fields turning up in the wrong place or disappearing altogether. Your job is to trace the mapping logic, patch whatever serializers, DTOs or query builders are responsible, and make sure every retrieval call returns the exact structure our front end expects. While you are in the code, please double-check adjacent workflow logic and edge-case paths so the system stops throwing inconsistent responses under unusual input. I will give you the repository, environment configuration and a staging server for live testing; just work on a feature branch, comment your fixes clearly, and keep the commit history tidy. Deliverables • Corrected data mapping on all data-retrieval endpoints • Added or updated unit/integration tests proving consistent responses • A brief changelog outlining what was fixed and how you validated it If you are comfortable diving straight into an existing codebase and turning this around quickly, I’m ready to hand over access as soon as you’re available.