Factual error: The plot's main conceit hinges upon coders, the art department, and the user-end network team constantly working live at the same time in the same room, as well as developers actively writing code, rebooting servers, and chasing players in-game to get rid of problematic players. No real game company could operate this way. Game content patches wouldn't change the network experience, and in-game aesthetic changes like the ones they make in seconds would require weeks if not months of development.
Other mistake: In the frame you can see the girl is playing on a newer Macbook, she is using a wired headset but the headset is not plugged into the laptop, you can also see she is using a wired gaming mouse, and the USB cable is just sitting there not connected to anything. The Macbook is USB-C only and the mouse is USB-A.
Continuity mistake: In Millie's Stash House, the first time you see the revolver Guy takes out, it is not cocked. Then, it is cocked. Then, it is not again. Then, it is. Then, not at the time he actually picks it up and cocks it. (00:26:38 - 00:27:02)
Other mistake: In the bank scene where Guy takes away the player's gun, the NPC who can't put his arms down is in the background with his hands on the counter.
Continuity mistake: Near the start during the 1st bank raid, his hands change position while lying down on the ground talking to the guard.
Suggested correction: As one of the principal developers of the simulation engine, Millie recognizes that Guy is a non-player character (NPC) who merely obeys a loop of coded actions, and he's supposedly incapable of acting outside of his code. So, she means that NPCs can't just arbitrarily kiss players. Players can do whatever they want, but NPCs are mindless robots. At that point, however, she doesn't realise that Guy's Artificial Intelligence has evolved to independent self-awareness, allowing him to act outside of his code.
Charles Austin Miller
Key's actually says "There isn't a button for that" when Millie brings it up. There would be no way for her to initiate, as her in game actions would be limited to the controls offered.
By the time Millie kisses Guy, we know that the Free City simulation engine was already undergoing Artificial Intelligence evolution, essentially rewriting its own code, allowing Guy (and other NPCs) to achieve independent self-awareness. It follows that Free City was probably rewriting its player code, as well, making all sorts of new and startling functions possible for players and NPCs alike.
Charles Austin Miller