Other mistake: Just before Arnold arrives at his brother Edward's apartment, he walks across a plaza. Note the people standing/sitting in the background, along the railing. They are still there, apparently not having moved an inch, in another scene of that plaza which is supposed to be much later after Arnold has been caught, sent to the tele-station and gassed unconscious. (00:14:20 - 00:26:20)
Other mistake: Damon, the game show host, is talking to an elderly lady who says she's rooting for Richards. Watch Damon's mouth. He's helping the actress by mouthing her words with her.
Other mistake: When everyone in the audience and everybody at the betting board see the original unedited version of what really happened at Bakersfield, it shows a soldier hitting Ben with the butt of his weapon from Ben's point of view, which is an impossible camera angle. And as it's the original unedited footage, it won't be something they faked.
Other mistake: When Killian's guard goes to enter his code to open the gate, it starts to open when he touches the first digit, rather than after the last digit.
Other mistake: In the opening sequence of the Huey flying over the crowd, the uniforms of all five men stay unruffled, despite the doors and windows being open, which would allow the wind to pass through.
Other mistake: The list of possible prisoners contestants the computer goes through shows different information, but the page with the 8 rows of double letters and numbers remains relatively the same, even though it's suppose to show variations and different information (i.e. AA always has -583 and -5483 and BB always has -484 and -4838).
Answer: When Ben is walking to the apartment door, he has a huge case with him which is big enough to hold clothes and even shaving equipment. Ben entered the door code into the keypad which unlocked the door so the code was never changed.