404 error after checkout

Hi..

I am having an issue when someone checks out with their bank deposit. The order goes through but the customer just gets a 404 error and doesn’t think the order went through.
It has been working great for the last 4-5 months since setting it up but i am not sure when this issue started happening. I am guessing it was from one of the last woo commerce updates.
As far as i know the paypal check out is ok.
Any help would be greatly appreciated.

http://www.oneclicktechnology.com.au/shop/

### Environment ###

Home URL: http://www.oneclicktechnology.com.au
Site URL: http://www.oneclicktechnology.com.au
WC Version: 2.1.12
WC Database Version: 2.1.12
WP Version: 3.9.1
WP Multisite Enabled: No
Web Server Info: Apache
PHP Version: 5.2.17
MySQL Version: 5.5.37
WP Memory Limit: 96 MB
WP Debug Mode: No
WP Language: Default
WP Max Upload Size: 10 MB
PHP Post Max Size: 10 MB
PHP Time Limit: 30
PHP Max Input Vars: 1000
SUHOSIN Installed: No
WC Logging: Log directory is writable.
Default Timezone: Default timezone is UTC
fsockopen/cURL: Your server has fsockopen and cURL enabled.
SOAP Client: Your server has the SOAP Client class enabled.
WP Remote Post: wp_remote_post() was successful – PayPal IPN is working.

### Locale ###

decimal_point: .
thousands_sep:
mon_decimal_point:
mon_thousands_sep:

### Plugins ###

Installed Plugins: BackupBuddy by Dustin Bolton version 4.0.1.4
0$ Woocommerce Product Feed by Victor Ciobanu version 0.35
Google Analytics Dashboard for WP by Alin Marcu version 4.3
Gravity Forms by rocketgenius version 1.7.6
WooCommerce Custom Product Tabs Lite by SkyVerge version 1.2.5
WooCommerce Google Analytics Integration by WooThemes version 1.1.0
WooCommerce ShareDaddy Integration by WooThemes version 1.0
WooCommerce by WooThemes version 2.1.12
Wordfence Security by Wordfence version 5.1.5
WordPress Importer by wordpressdotorg version 0.6.1
WordPress SEO by Joost de Valk version 1.5.4.2

### Settings ###

Force SSL: No

### WC Pages ###

Shop Base: #286 – /shop/
Cart: #287 – /cart/
Checkout: #288 – /checkout/
My Account: #289 – /my-account/

### WC Taxonomies ###

Order Statuses: cancelled (cancelled)
completed (completed)
failed (failed)
on-hold (on-hold)
pending (pending)
processing (processing)
refunded (refunded)

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

### Theme ###

Theme Name: Enfold Child
Theme Version: 1.0
Author URL: http://www.kriesi.at

### Templates ###

Template Overrides: No overrides present in theme.

https://wordpress.org/plugins/woocommerce/