In this section of the guide to Layers of Fear 2, you can find a description of the second puzzle with the lock, which is solved during the passage of the second act of the game. You have to read the combination from the rotating board and enter it into the locked door.
You will encounter the locked door with a lock shortly after solving the second puzzle with the projector.
Check the surrounding cabins. In one of them, there is a blackboard. Press it to get rotated 180 degrees. The code is 482.
You can already return to the lock and enter the code 482.