I ran a dedupe check on my own contacts (about 2,400 numbers, mostly US and Italy) and hit something I can't fix cleanly.

566 of them have no country code, so whatever normalizes them has to guess one. For 46 of those, both guesses give a valid number. A ten digit number starting with 347 is a New York number and also an Italian Vodafone mobile. 339, 330 and 320 do the same thing. libphonenumber calls it valid either way, so validation never catches the wrong pick, and 41 of those cards had no other number on them to go by.

I build a contacts export app (Contact Exporter) and ran into this while testing its cleanup step.

Where does yours take the default country from? The user's locale, the account's country, the contact's address? And does anything flag a number that's valid in two places?