Coupon – Incorrect Percentage Calculation

I think there’s a bug with the current version of WooCommerce.
I have also tried turning off all plugins besides WooCommerce and setting a flat-rate using Woo.

Issue:
When a coupon code is applied after the the shipping amount gets calculated then the percentage is calculated incorrectly.

For example, using a 30% off coupon.
Price of product = $21
After coupon = 14.70
This is Correct – https://prntscr.com/lny0lq

However, when the user clicks on checkout, enters their address and has shipping applied (flat-rate) it is incorrect.

Product = $21
Shipping = $4.95
After Coupon = $19.65 which is incorrect. (should be $18.17)
The coupon also shows: -$6.30 which is also incorrect (should be $7.79)
https://prntscr.com/lny1z5

Now that shipping has been applied, even if the user hits back or clicks on the link to go to cart the calculations is still the same.
If the product is removed and another product is added shipping is still calculated on-top of that product and therefore the coupon discount is still calculated wrong.
Example:
8 + 4.95 = 12.95
https://prntscr.com/lny30h

30% coupon should equal a total of $9.07 (save $3.89) but it shows a total of $10.55 with $2.40 off.
https://prntscr.com/lny3c1

### WordPress Environment ###

Home URL: https://www.theislandtraveller.com
Site URL: https://www.theislandtraveller.com
WC Version: 3.5.1
Log Directory Writable: ?
WP Version: 4.9.8
WP Multisite: –
WP Memory Limit: 512 MB
WP Debug Mode: ?
WP Cron: ?
Language: en_AU
External object cache: –

### Server Environment ###

Server Info: LiteSpeed
PHP Version: 7.0.32 - We recommend using PHP version 7.2 or above for greater performance and security. How to update your PHP version
PHP Post Max Size: 128 MB
PHP Time Limit: 300
PHP Max Input Vars: 10000
cURL Version: 7.60.0
OpenSSL/1.0.2k

SUHOSIN Installed: –
MySQL Version: 10.1.36-MariaDB-cll-lve
Max Upload Size: 128 MB
Default Timezone is UTC: ?
fsockopen/cURL: ?
SoapClient: ?
DOMDocument: ?
GZip: ?
Multibyte String: ?
Remote Post: ?
Remote Get: ?

### Database ###

WC Database Version: 3.5.1
WC Database Prefix: wp_
MaxMind GeoIP Database: ?
Total Database Size: 5.32MB
Database Data Size: 4.27MB
Database Index Size: 1.05MB
wp_woocommerce_sessions: Data: 0.02MB + Index: 0.00MB
wp_woocommerce_api_keys: Data: 0.00MB + Index: 0.00MB
wp_woocommerce_attribute_taxonomies: Data: 0.00MB + Index: 0.00MB
wp_woocommerce_downloadable_product_permissions: Data: 0.00MB + Index: 0.00MB
wp_woocommerce_order_items: Data: 0.00MB + Index: 0.00MB
wp_woocommerce_order_itemmeta: Data: 0.01MB + Index: 0.02MB
wp_woocommerce_tax_rates: Data: 0.00MB + Index: 0.00MB
wp_woocommerce_tax_rate_locations: Data: 0.00MB + Index: 0.00MB
wp_woocommerce_shipping_zones: Data: 0.00MB + Index: 0.00MB
wp_woocommerce_shipping_zone_locations: Data: 0.00MB + Index: 0.00MB
wp_woocommerce_shipping_zone_methods: Data: 0.00MB + Index: 0.00MB
wp_woocommerce_payment_tokens: Data: 0.00MB + Index: 0.00MB
wp_woocommerce_payment_tokenmeta: Data: 0.00MB + Index: 0.00MB
wp_woocommerce_log: Data: 0.00MB + Index: 0.00MB
wp_adtribes_my_conversions: Data: 0.00MB + Index: 0.00MB
wp_auto_updates: Data: 0.00MB + Index: 0.00MB
wp_commentmeta: Data: 0.31MB + Index: 0.21MB
wp_comments: Data: 0.18MB + Index: 0.13MB
wp_links: Data: 0.00MB + Index: 0.00MB
wp_litespeed_img_optm: Data: 0.00MB + Index: 0.00MB
wp_litespeed_optimizer: Data: 0.00MB + Index: 0.00MB
wp_options: Data: 0.91MB + Index: 0.05MB
wp_postmeta: Data: 2.15MB + Index: 0.47MB
wp_posts: Data: 0.65MB + Index: 0.08MB
wp_termmeta: Data: 0.00MB + Index: 0.01MB
wp_terms: Data: 0.00MB + Index: 0.01MB
wp_term_relationships: Data: 0.01MB + Index: 0.02MB
wp_term_taxonomy: Data: 0.00MB + Index: 0.01MB
wp_usermeta: Data: 0.01MB + Index: 0.01MB
wp_users: Data: 0.00MB + Index: 0.01MB
wp_wc_download_log: Data: 0.00MB + Index: 0.00MB
wp_wc_webhooks: Data: 0.00MB + Index: 0.00MB
wp_wpmfs_queue: Data: 0.02MB + Index: 0.02MB
wp_xcloner_scheduler: Data: 0.00MB + Index: 0.00MB
wp_yikes_easy_mc_forms: Data: 0.00MB + Index: 0.00MB

### Post Type Counts ###

attachment: 182
nav_menu_item: 9
nectar_slider: 1
page: 19
post: 2
product: 17
product_variation: 112
revision: 40
shop_coupon: 1
shop_order: 3
wcct_countdown: 1
wpcf7_contact_form: 2

### Security ###

Secure connection (HTTPS): ?
Hide errors from visitors: ?Error messages should not be shown to visitors.

### Active Plugins (30) ###

Aliexpress Dropship for Woocommerce: by MA-Group – 1.5.1 – Not tested with the active version of WooCommerce
Auto Image Attributes From Filename With Bulk Updater: by Arun Basil Lal – 1.5
The SEO Framework: by Sybre Waaijer – 3.1.4
Blackhole for Bad Bots: by Jeff Starr – 2.1
Block Bad Queries (BBQ): by Jeff Starr – 20181117
Companion Auto Update: by Papin Schipper – 3.3.1
Contact Form 7: by Takayuki Miyoshi – 5.0.5
Enable Media Replace: by ShortPixel – 3.2.7
Enhanced E-commerce for Woocommerce store: by Tatvic – 2.1.4
Instagram Feed: by Smash Balloon – 1.10.2
Salient WPBakery Page Builder: by Michael M - WPBakery.com | Modified by ThemeNectar – 5.5.2
Limit Login Attempts Reloaded: by wpchefgadget – 2.7.1
My Custom Functions: by Space X-Chimp – 4.31
PayPal for WooCommerce: by Angell EYE – 1.5.3
PixelYourSite: by PixelYourSite – 5.3.2 – Not tested with the active version of WooCommerce
Revision Control: by Dion Hulse – 2.3.2
Category Order and Taxonomy Terms Order: by Nsp-Code – 1.5.5
The SEO Framework - Extension Manager: by Sybre Waaijer – 2.0.0
TWB Woocommerce Reviews: by Abu Bakar – 1.6 – Not tested with the active version of WooCommerce
WooCommerce Weight Based Shipping: by weightbasedshipping.com – 5.2.1 – Not tested with the active version of WooCommerce
Product Feed PRO for WooCommerce: by AdTribes.io – 3.8.9
WooCommerce Stripe Gateway: by WooCommerce – 4.1.13
WooCommerce Variation Swatches Images: by ma_group – 1.0.2 – Not tested with the active version of WooCommerce
WooCommerce: by Automattic – 3.5.1
WP Fastest Cache: by Emre Vona – 0.8.8.8
WP Sitemap Page: by Tony Archambeau – 1.6.1
XCloner - Site Backup and Restore: by Liuta Ovidiu – 4.0.9
Easy Forms for MailChimp: by YIKES
Inc. – 6.4.10

### Settings ###

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

Taxonomies: Product Visibility: exclude-from-search (exclude-from-search)
exclude-from-catalog (exclude-from-catalog)
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: #6184 - /shop/
Cart: #6185 - /cart/
Checkout: #6186 - /checkout/
My account: #6187 - /my-account/
Terms and conditions: ? Page not set

### Theme ###

Name: The Island Traveller
Version: 0.1
Author URL: https://PeterStavrou.com
Child Theme: ?
Parent Theme Name: Salient
Parent Theme Version: 9.0.1
Parent Theme Author URL: https://themeforest.net/user/themenectar
WooCommerce Support: ?

### Templates ###

Overrides: salient/woocommerce/checkout/form-checkout.php version 2.3.0 is out of date. The core version is 3.5.0
salient/woocommerce/checkout/review-order.php
salient/woocommerce/checkout/terms.php
salient/woocommerce/content-product.php
salient/woocommerce/content-single-product.php
salient-child/woocommerce/emails/customer-processing-order.php
salient/woocommerce/loop/add-to-cart.php
salient/woocommerce/loop/loop-start.php
salient/woocommerce/myaccount/form-login.php version 3.4.0 is out of date. The core version is 3.5.0
salient/woocommerce/single-product/product-image.php version 3.3.2 is out of date. The core version is 3.5.1
salient/woocommerce/single-product/tabs/description.php
salient/woocommerce/single-product/tabs/tabs.php

The page I need help with: [log in to see the link]