I worked for a company that.. Used msql sever a lot and we would run into a heisenbug every few months that would crash our self hosted msql server cluster or it would become unresponsive. I'm not a database person so I'm probably butchering the description here. From our POV progress would stop and require manual intervention (on call). Back and forth went on with MS and our DBAs for YEARS pouring over logs or whatever they do.. Honestly never thought it would be fixed. Then one time it happened and we caught all the data going into the commit and realized it would 100% reproduce the crash. Only if we restored the database to a specific state and with this specific commit it would crash MS SQL Server. NDAs were signed and I took machete to our code base to create a minimal repro binary that could deserialize our data store and commit / crash MS SQL sever. Made a nice powershell script to wrap it and repro the issue fast and guess what? Within a month they fixed it. Was never clear on what exactly the problem was on their end.. I got buffer overflow vibes, but that's a guess.

Wow, that's pretty epic and satisfying