Issue with plugin

Hi guys,
The checkout API calls are very very slow, and we are on an Australian VPS with 4 cores and 8 gig ram.
This really needs looking into.
also, we found an issue where a customer can put a postcode in(on the checkout page), and not choose a suburb, but still checkout.
Here is a link to a vid showing the issue: https://www.dropbox.com/s/x9jjfp9xbt3vgl5/screen-capture.webm?dl=0