I have encountered this problem as well, and after consulting my friend who works in the phone repair industry I discovered it’s apparent source as well as why it seems common among us. When replacing the charging port one of the screws (the one that is inserted through the small plastic piece covering the charging port) must be inserted with care as the screw is slightly too long. If fully tightened it will actually damage the screen.
If you reopen the phone, you may notice that this line occurs perfectly aligned with the screw in question. I’m not sure if it was intentionally designed this way or not as an anti-repair element but it’s something you should look out for. I’m going to be replacing the screen soon and will update with my findings. I may not even replace the screw as it risks damage to the screen.
Someone might get lucky by loosening the screw, but I fear that usually when this line appears it is irreparable.