Not the poster you asked, but a lot of times the address boxes will "help" you buy parsing what you write and correcting it. Maybe his penthouse address gets corrected to the second line and USPS delivers it incorrectly.
My personal issus are the apartment selectors. I live in a complex with about 300 units and having to scroll all the way to the bottom is a huge pain in the ass. lol
I don't know if this would be useful in your case, and it's desktop only, but in the UK because the convention is to have the house/apartment/anything number at the start of the line when I need to choose my address from a dropdown box I select the field, then type my numbers and it selects the right one. This works for dropdown boxes in general where you know the first letters/characters you are looking for (but I can imagine scenarios where it would be no hope, like if all the addresses are written with the differentiating number/detail at the end not the start). Page down / end keys are also useful for long lists (again, not so helpful on mobile).
I live in Los Altos Hills but online correction software sees the zip (which we share) and corrects it to Los Altos, the next town over. This often causes confusion.
My personal issus are the apartment selectors. I live in a complex with about 300 units and having to scroll all the way to the bottom is a huge pain in the ass. lol