[As an experienced Local Guide, I now sometimes come across inconsistencies or notice that errors have been made that I used to make myself when I started out. So I am publishing a few 'best practice' posts, in the hope it can help others.]
A short tip, this time, but a useful one, as it will prevent you from unintentionally adding incorrect data.
Sometimes you might want to add a point of interest (POI) which does not have a house number, e.g. a tourist attraction or viewing point, a statue or a glass recycling container. In those cases, the main thing you should know is that you should not enter the ZIP code when entering the address. If you do enter it, the algorithm will interpret the number you entered as the house number and then add that same number once more as ZIP code. You then end up with something like 'Main Street 1234, 1234 Anytown'. If you enter only street name and town, it will get created correctly as 'Main Street, 1234 Anytown'.