Strange Shipping Zone issue at checkout for website user

My wordpress woocommerce site is https://www.kablooiestore.com.au

Here is my system status report for woocommerce

### WordPress Environment ###

Home URL: https://kablooiestore.com.au
Site URL: https://kablooiestore.com.au
WC Version: 2.6.8
Log Directory Writable: ?
WP Version: 4.6.1
WP Multisite: –
WP Memory Limit: 256 MB
WP Debug Mode: –
WP Cron: ?
Language: en_US

### Server Environment ###

Server Info: Apache
PHP Version: 5.6.27
PHP Post Max Size: 64 MB
PHP Time Limit: 30
PHP Max Input Vars: 1000
cURL Version: 7.24.0
OpenSSL/1.0.0

SUHOSIN Installed: –
MySQL Version: 5.6.32
Max Upload Size: 64 MB
Default Timezone is UTC: ?
fsockopen/cURL: ?
SoapClient: ?
DOMDocument: ?
GZip: ?
Multibyte String: ?
Remote Post: ?
Remote Get: ?

### Database ###

WC Database Version: 2.6.8
: 
woocommerce_sessions: ?
woocommerce_api_keys: ?
woocommerce_attribute_taxonomies: ?
woocommerce_downloadable_product_permissions: ?
woocommerce_order_items: ?
woocommerce_order_itemmeta: ?
woocommerce_tax_rates: ?
woocommerce_tax_rate_locations: ?
woocommerce_shipping_zones: ?
woocommerce_shipping_zone_locations: ?
woocommerce_shipping_zone_methods: ?
woocommerce_payment_tokens: ?
woocommerce_payment_tokenmeta: ?

### Active Plugins (21) ###

AfterShip - WooCommerce Tracking: by AfterShip – 1.6.6
Akismet: by Automattic – 3.2
Breadcrumb NavXT: by John Havlik – 5.5.2
Contact Form 7: by Takayuki Miyoshi – 4.5.1
Google Analytics by MonsterInsights: by MonsterInsights – 5.5.4
Jetpack by WordPress.com: by Automattic – 4.3.2
MailChimp for WordPress: by ibericode – 4.0.7
MailChimp for WordPress - Top Bar: by ibericode – 1.2.15
Meta Slider: by Matcha Labs – 3.3.7
MOJO Marketplace: by Mike Hansen – 1.0.4
Page Builder by SiteOrigin: by SiteOrigin – 2.4.18
SiteOrigin Widgets Bundle: by SiteOrigin – 1.7.2
UpdraftPlus - Backup/Restore: by UpdraftPlus.Com
DavidAnderson – 1.12.25

Instagram Feed WD: by WebDorado – 1.1.14
Abandoned Cart Lite for WooCommerce: by Tyche Softwares – 3.2
WooCommerce Advanced Free Shipping: by Jeroen Sormani – 1.0.11
WooCommerce Category Banner: by WP BackOffice – 1.1.2
WooCommerce Stripe Gateway: by Automattic – 3.0.6
WooCommerce: by WooThemes – 2.6.8
Wordfence Security: by Wordfence – 6.2.5
Yoast SEO: by Team Yoast – 3.8

### Settings ###

Force SSL: ?
Currency: AUD ($)
Currency Position: left
Thousand Separator: ,
Decimal Separator: .
Number of Decimals: 2

### API ###

API Enabled: ?

### WC Pages ###

Shop Base: #5 - /shop/
Cart: #6 - /cart/
Checkout: #7 - /checkout/
My Account: #8 - /my-account/

### Taxonomies ###

Product Types: external (external)
grouped (grouped)
simple (simple)
variable (variable)

### Theme ###

Name: FreeStore
Version: 1.1.7
Author URL: https://kairaweb.com/
Child Theme: ? – If you're modifying WooCommerce on a parent theme you didn't build personally
then we recommend using a child theme. See: How to create a child theme

WooCommerce Support: ?

### Templates ###

Overrides: –

So I have searched the forum and cant find this exact issue. It may not be resolvable as is only thru feedback from a customer using my website. I cannot replicate the problem myself. I have also had another user test on another computer and they couldn’t replicate the problem either!

issue – I have a free shipping code set up on my site, for a limited time. It is valid in Australia, but I have not enabled free shipping in either North America or the rest of the world, so it doesn’t work for these zones.
I had an Australian customer send me series of screen shots showing that she was attempting to purchase, had her country set as Australia in her address, but the shipping cost is coming up as ‘rest of the world’ shipping, which cost much more, and the free shipping code isn’t working.
(I also have the checkout set to not show any default shipping until the address has been entered)

She emptied cart and tried several times on different devices and had the same result each time.
I changed the rest of the world shipping to allow free postage and it then allowed her to choose this option – which suggests it was definitely treating her as if her address was outside of Australia. Is there any way that this could be happening? I cant get it to happen for me when I try. I’m just concerned that it may be happening to other customers who are not letting me know.

Thanks so much – any advice would be much appreciated – let me know if I need to provide more information….
Also, once I modified the rest of the world shipping, she tried to pay for the transaction – after entering credit card details, website tried to load/think and then seemed to reset and the details she had entered just disappeared – she sent me a short video of this happening.