Asking valid postcode / ZIP with some countries

Hi,
My shipping calculator seams to be nuts the last few days. I’ve very straight forward rules for shipping calculation;
1) Free delivery for all eu countries
2) Rest of the world < 0.5Kg
3) Rest of the world 0.5-1Kg
4) Rest of the world +1Kg

When you go to the cart to calculate the shipping, it doesn’t work for certain countries, asking to enter a valid postcode? “Please enter a valid postcode / ZIP.”

https://www.ukinkalla.com (add something to the cart before!)
For example, Australia works fine but not with Canada, USA, etc… It asks for a valid postcode. Even for EU countries like Spain, it doesn’t recognize it as Free delivery, asking again for a “valid postcode”.

Any ideas for a work around?
Cheers,
Desiree