Years ago we had been developing a game for the handheld consoles. We were very young && inexperienced back then. Some more than others... Version for one of the consoles finally saw the light of day, while the other one was sadly canceled.
The development of that canceled one was very troubled.
One example of that would be the core team during the initial stages of the project. One fairly seasoned programmer... Yes - that's it.
Obviously he needed some help, so... the studio hired interns. Two of them, IIRC. One of the interns was put in charge of the game's multiplayer code.
He was ostensibly doing a good job, as the mode was working. Sure it needed some fixing && some tweaks, but it was there.
That is until it came time to check the platform's requirements by the testers. By the time they got their hands on the documentation, it turned out that the SDK used by the game had become obsolete && was no longer eligible for submission. Once the SDK was updated to a newer version, the multiplayer stopped working for some reason.
The issue was investigated which revealed that the intern who wrote the code had been using functions that were marked as deprecated && were no longer available in the newer SDK, explaining why the mode was FUBAR.
Moral of the story? Pay close attention to:
0. Interns,
1. Platform's requirements,
2. Changelogs,
3. Deprecations.