This has been mentioned in the forums
Here: https://www.halowaypoint.com/en-us/forums/84ad72a8b51847978545f685f651fc15/topics/halo-4-reclaimer-level-game-breaking-bug/af9a820c-5ee0-46c0-a267-87ca9d97d5de/posts
and here: https://www.halowaypoint.com/en-us/forums/85d779d52cfd46918b4f8b638f2e3c7b/topics/halo-4-reclaimer-mammoth-glitch/a93f8c3f-822c-46e4-8fa7-0d32f1730355/posts?page=1
But not in the support section so I am posting it here in hopes that a 343 member sees it and gets it patched. Here’s the problem/issue/bug:
In the level “Reclaimer” of Halo 4 you are required to go up into a gravity lift and destroy a Lich drop ship. Upon going up and destroying the reactor, the Lich spirals out of control. It’s shield glows and it stops in mid air and that is all. The ship doesn’t explode but the rest of game dialogue go on as normal. As the Mammoth continues and at about the same point that Cortana and the Chief start talking about here rampancy due to her outburst, the rest of the level then fails to render/load. The Mammoth drives off into/onto nothingness and you are ripped out of the Mammoth. It doesn’t matter if you are on it or in it. You are left floating in air and the Mammoth eventually stops. The game fails to progress and you can’t proceed.
I and other players have tried reloading the last checkpoint, but this simply reloads to where the Lich is supposed to explode and fails to. The only work around is to restart the level and hope that the same problem does not occur. This bug is particularly frustrating due to the amount of time it takes to get to this point in the level. Not to mention you are unable to proceed.