The best times are when US ecommerce sites try to confidently lint foreign addresses, even when they allow shipping there.

I've had them tell me I need 5 digits for my postal code in Norway, which uses 4 digits. I selected Norway in the shipping web form.

Or when they tell me special characters aren't allowed, yet the "special characters" are just letters in the Norwegian alphabet. My address contains ø. These aren't even unicode, they're in the extended 8 bit ascii set. Why are you linting these!?

These happen all the time. Thankfully our postal system recognises this and allows some substitutions (å=aa, ø=oe, æ=ae).