So there's a scene in wonderful film Double Indemnity which doesn't make a lick of sense. Barbara Stanwyck is coming to meet Fred MacMurray to discuss the latest phase of their nefarious scheme, only to hear through the door that Fred MacMurray already has company - Edward G. Robinson, better known to some as the original Chief Wiggum! They're discussing the insurance settlement that Barbara has cheated the company out of!
So she's put in something of an awkward position. Edward could be leaving at any moment, so she really should run - but then again, it's vitally important that she hear what's going on inside the room! Finally she waits too long, and the door opens-
But she's able to hide behind it? Yes, unlike every other apartment building in the history of America, the door to the private apartment opens out into the communal hallway. In an amazing coincidence, this gives her an opportunity to hide while Fred is seeing Edward off.
So why this bizarre bit of staging? Couldn't they have just built the hallway with alcoves for her to duck into, and Fred to stand in front of? Probably just a function of limited time and budget, like most other errors of this type. Wilder wrote it into the script, then when he saw it in action, he was smart enough to realize how false it looked, but understood that it would cost more to fix than it was worth, since most people would never even notice what was off about the scene.
Well, I noticed, Billy Wilder. Me, a guy watching the movie 72 years after you made it and then spent decades being universally praised for its quality.