As noted by a number of players, the code on the first door would reset every time you looked at the phone, which was annoying, since you needed to look at the phone to solve the puzzle.

It turns out this was actually worse than it sounded. The actual code wasn't reset, just the appearance of the buttons, so the code the player saw and the code the game 'saw' were actually different. Clicking on any of the buttons would cause that button to resync, so its possible to get through the door if the player only ever clicks the buttons that ought to be on. This meant that the following sequence would get through the door successfully:

1. Click correct button 1
2. Check phone
3. Click correct button 1 again, think the click didn't work
4. Click correct button 1 again, see it work this time
5. Click remaining correct buttons

Whereas this sequence would leave the player trapped forever:

1. Click incorrect button
2. Check phone, realise button was incorrect
3. Assume button had reset to off, when it was actually secretly on
4. Never click the button again, because you think it is off
5. Click correct buttons, visually observe the correct code
6. Game still thinks incorrect button is enabled, doesn't let you through the door

I've now updated the game to correctly remember (both game state and visually) the code entered, which both fixes the bug and makes it easier for the players.