This is because there seems to have a been a mix up between the game's developers, Undead Labs and Microsoft leading to the patch not properly being applied.
Jeff Strain, the game's Executive Producer issued a statement on the game's forums earlier today, apologising for the mistake.
He said the studio has been tracking the bug across the weekend, initially suspecting it to be an occasional problem but eventually realising that "the people reporting improvements simply had good luck, not a fixed game".
Although he "doesn't have an ETA on a solution", as Undead Labs "can't directly fix the problem", the studio is "calling in the troops" to try and help Microsoft get the correct version live.
"Although we can't directly fix the problem, you are OUR players, and we'd like you to know we're exploring ways to express our appreciation for your patience."
Strain said that if the worst comes to worst, the team can roll the fixes from Title Update 1 into the upcoming Title Update 2, which looks to fix the 'eternal loading' bug.
Thanks, Game Informer.