Order with wrong shipping cost

Hi there

I’m using the latest woocommerce version with 3 shipping zones UK, EU and Rest of the world.
www. itshandmade.co.uk/

Since I set it up, I’ve had 2 orders with the wrong shipping costs. Clients checked out and add paid for Europe standard delivery when it should have been free.

I can’t replicate the problem and it doesn’t happen with all clients.

Any idea?

Many thanks

https://www.ads-software.com/plugins/woocommerce/