Hi guys, this is the problem I got during this issue.
I tried using 3 zone of UK country, but if do search a specific postcode, it only shows the Mainland UK shipping method.
Example if I search a postcode near in Northern Ireland, I expected to see Standard Delivery shipping method only but Mainland UK shipping method is showing as always.
See the image below on how it look like on my admin setup.
To make it work, I just simply drag Mainland UK as my last zone (before rest of the world). Then searching a specific shipping zone is fix. I spent so much time looking at the issue but thanks to http://stackoverflow.com for helping me to solve the issue.
Happing WordPress everyone. 🙂