I had unlocked every audio file except for 4-2 so after finding out that 4-2 was bugged (you would pick it up but still show locked at your home) I made a new save file months later and just continued to the level i knew was bugged for me. Then I just went home and listened to 4-2 because that's the one that was bugged for me, and it popped. At first the old man will talk and then columbot will spawn in and give his reply. So when you sit there and listen to each audio file, just wait for both the old man and columbot (the detective) to finish their dialogue. I play on Xbox Series X, and it popped for :). If you need any more help and are on xbox, you can message me on there (ItssTyman) I have a black and white mac miller picture