Order status on hold or completed, should be processing

### EXPLANATION OF THE ISSUE

Using woocommerce 3.0.5.

Some orders are coming in as ‘cancelled’, ‘on hold’ or ‘completed’ where they should be marked as ‘processing’. Currently we manually check the payments in Omnikassa (the payment provider) and then change the status to ‘processing’. However the correct order status should automatically be chosen by woocommerce, so that the customer gets an order confirmation and our warehouse can process the order.
I have already called omnikassa and they are saying the problem is caused by woocommerce

<!– What happens, under which versions, under what conditions, when, and what were you expecting instead. –>

### STEPS TO REPRODUCE THE ISSUE

Placing orders will sometimes result in a replication, but not always.

<!– 1. List steps to reproduce your issue so we can replicate. –>

### SYSTEM STATUS

<details>
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Grab the system status report from WooCommerce > System Status and paste it here between the details tags.
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### WordPress Environment ###

Home URL: https://freshwatervalley.nl
Site URL: https://freshwatervalley.nl
WC Version: 3.0.5
Log Directory Writable: ?
WP Version: 4.7.4
WP Multisite: –
WP Memory Limit: 1 GB
WP Debug Mode: –
WP Cron: ?
Language: en_US

### Server Environment ###

Server Info: Apache
PHP Version: 5.6.22
PHP Post Max Size: 50 MB
PHP Time Limit: 600
PHP Max Input Vars: 5000
cURL Version: 7.36.0
OpenSSL/1.0.1e

SUHOSIN Installed: –
MySQL Version: 5.6.35
Max Upload Size: 50 MB
Default Timezone is UTC: ?
fsockopen/cURL: ?
SoapClient: ?
DOMDocument: ?
GZip: ?
Multibyte String: ?
Remote Post: ?
Remote Get: ?

### Database ###

WC Database Version: 3.0.5
WC Database Prefix: wp_
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: ?

### Security ###

Secure connection (HTTPS): ?
Hide errors from visitors: ?

### Active Plugins (28) ###

Polylang: by Frédéric Demarle – 2.1.3
AdRoll for WooCommerce Stores: by AdRoll – 1.0.2
Instant Search + for WooCommerce Search: by Fast Simon Inc – 1.8.1
MailChimp: by MailChimp – 1.5.7
Order / Coupon / Subscription Export Import Plugin for WooCommerce (BASIC): by XAdapter – 1.1.9
PixelYourSite: by PixelYourSite – 5.0.2
Pronamic Pay: by Pronamic – 4.6.0
PushCrew: by Wingify Software Pvt Ltd – 1.1
Really Simple SSL: by Rogier Lankhorst – 2.5.13
Smart Offers: by StoreApps – 3.2.8
Tidio Chat: by Tidio Ltd. – 3.0.2
Tracking Code Manager: by IntellyWP – 1.11.1
UpdraftPlus – Backup/Restore: by UpdraftPlus.Com
DavidAnderson – 2.12.40.1

WooCommerce Product Feed: by WebAppick – 2.0.16
Webgains Ads Widget: by Joseph Nguyen – 1.5.1
Advanced Order Export For WooCommerce: by AlgolPlus – 1.3.0
WooChimp: by RightPress – 2.2.1
WooCommerce Bulk Discount: by Rene Puchinger – 2.4.5
Woocommerce bulk percentage pricing: by Hussam Hussien – 2.1.3
WooCommerce Export Customer Email: by MH Mithu – 1.3
WooCommerce AdWords Conversion Tracking: by Wolf+B?r GmbH – 1.3.5
WooCommerce Google Analytics Integration: by WooCommerce – 1.4.1
WooCommerce AdWords Dynamic Remarketing: by Wolf + B?r GmbH – 1.3.3
WooCommerce PDF Invoices & Packing Slips: by Ewout Fernhout – 1.6.5
WooCommerce: by Automattic – 3.0.5
WordPress Importer: by wordpressdotorg – 0.6.3
WP All Import: by Soflyy – 3.4.3
WP-PageNavi: by Lester ‘GaMerZ’ Chan – 2.91

### Settings ###

API Enabled: ?
Force SSL: –
Currency: EUR (€)
Currency Position: left
Thousand Separator: ,
Decimal Separator: .
Number of Decimals: 2
Taxonomies: Product Types: external (external)
grouped (grouped)
simple (simple)
variable (variable)

Taxonomies: Product Visibility: exclude-from-catalog (exclude-from-catalog)
exclude-from-search (exclude-from-search)
featured (featured)
outofstock (outofstock)
rated-1 (rated-1)
rated-2 (rated-2)
rated-3 (rated-3)
rated-4 (rated-4)
rated-5 (rated-5)

### WC Pages ###

Shop base: #5 – /?page_id=5&lang=en
Cart: #6 – /?page_id=6
Checkout: #7 – /?page_id=7
My account: #8 – /?page_id=8

### Theme ###

Name: Customizr Child
Version: 1.0.0
Author URL: https://themesandco.com
Child Theme: ?
Parent Theme Name: Customizr
Parent Theme Version: 3.4.36 – 3.5.11 is available
Parent Theme Author URL: https://presscustomizr.com/
WooCommerce Support: ?

### Templates ###

Overrides: customizr-child/woocommerce/emails/admin-new-order.php
customizr-child/woocommerce/loop/loop-start.php

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