This can also cause delivery failures the other way around - a friend in Germany once sent me a package but didn't bother writing the apartment number on it because she assumed the postman would use my name to find the right box. Instead it got sent right back to Germany. (Austrian bureaucracy is just as unforgiving as German, they just have different rules to follow...)
Surely enough, 2 days later I received the mail back at my mailbox. Wasted 2 euros ¯\_(ツ)_/¯
I just needed a single stamp, but they stamped on both so I couldn't even try to reuse it. And I also posted on the mailbox for "other zip code" rather than "close by zip codes".
I don't know if OCR or a person messed up. Well, definitely a person (me)...