Debug Existing Python Application

I have a working Python project that suddenly throws errors I can’t trace. The core logic is already in place; I only need the faults located and corrected so the program runs reliably again. I’ll provide the full source, a brief rundown of the expected behaviour, and sample data that triggers the failure. What I’m looking for: • Careful diagnosis of the stack-trace and any hidden edge-case issues • Clean, well-commented fixes that slot straight back into my repo without breaking current features • A short summary of the changes so I know exactly what was altered and why I use Git for version control, so please be comfortable working on a feature branch and submitting a pull request. If you lean on tools like pdb, pytest, logging, or linters such as flake8 to verify stability and code quality, that’s a plus. Once the patch runs error-free on my end and all existing functionality passes, the job is done. Let me know your availability and how soon you can start digging in.