Part of my responsibilities at Microsoft was to assist developers by jumping in and working on a feature or section of code that they need help with to ship their product. For three months leading up to launch I assisted Bungie with stability, performance, and rendering issues that threatened the release date.
The most significant issue was a bug that prevented the ability to reliably save files to the hard disk (notably saved games and player generated movies). The fix required both game engine and platform file system work due to the amount of content constantly generated and streamed by the title.
