# Incident Drill: 'Model X Hallucinated Yesterday' — Root-Cause Matrix

> Source: https://sukruyusufkaya.com/en/learn/fine-tuning-cookbook/ftc-incident-drill-root-cause
> Updated: 2026-05-14T14:43:02.370Z
> Category: Fine-Tuning Cookbook (Model-by-Model)
> Module: Part XVI — Production Operations
**TLDR:** Most-feared sentence in production: 'Model is returning garbage'. Cookbook's systematic root-cause matrix: model version change, base model update, API provider deprecation, dataset poisoning, prompt injection, sampling temp config drift. Incident response playbook, blameless postmortem template.