WooCommerce Custom Shipping Methods Removing Each Other - wordpress

Question

I have created 2 basic shipping methods in 2 different plugins, each plugin are below, one is Royal Mail the other is Courier. They both show up in the drop down in the shipping zone:
I can then add say Royal Mail to the zone, but if i now come to add Courier as well, Royal Mail disappears and vice versa, it's only letting me add one of my custom methods at a time and i'm stumped as to why.
The next problem is, when i delete one of my custom methods and hit save, i'm getting this fatal error and it doesn't remove, as far as i can see both of these classes are done correctly to the point they are at:
[14-Dec-2021 13:54:59 UTC] PHP Fatal error: Uncaught Error: Call to a
member function get_instance_option_key() on bool in
/Volumes/Work/project/public_html/wp-content/plugins/woocommerce/includes/class-wc-ajax.php:2923
add_action( 'woocommerce_shipping_init', function() : void {
/**
* Class Utterly_Courier_Shipping_Method
*/
class Utterly_Courier_Shipping_Method extends WC_Shipping_Method
{
/**
* Utterly_Royal_Mail_Shipping_Method constructor.
*/
public function __construct()
{
$this->id = 'utterly_courier';
$this->method_title = 'Courier delivery (Tracked & Signed)';
$this->method_description = 'Shipping via Courier';
$this->supports = [
'shipping-zones'
];
$this->init();
$this->enabled = 'yes';
$this->title = 'Courier delivery (Tracked & Signed)';
}
/**
*
*/
public function init() : void
{
$this->init_form_fields();
$this->init_settings();
// Save settings in admin if you have any defined
add_action( 'woocommerce_update_options_shipping_' . $this->id, array( $this, 'process_admin_options' ) );
}
/**
*
*/
public function init_form_fields() : void
{
parent::init_form_fields();
}
/**
* #param array $package
*/
public function calculate_shipping($package = [])
{
$rate = array(
'id' => $this->id,
'label' => $this->title,
'cost' => 10
);
$this->add_rate( $rate );
}
}
});
add_filter( 'woocommerce_shipping_methods', function( array $methods ) : array {
$methods['utterly_courier'] = 'Utterly_Courier_Shipping_Method';
return $methods;
});
add_action( 'woocommerce_shipping_init', function() : void {
/**
* Class Utterly_Royal_Mail_Shipping_Method
*/
class Utterly_Royal_Mail_Shipping_Method extends WC_Shipping_Method
{
/**
* Utterly_Royal_Mail_Shipping_Method constructor.
*/
public function __construct()
{
$this->id = 'utterly_royal_mail';
$this->method_title = 'Royal Mail 1st Class (Tracked)';
$this->method_description = 'Shipping via Royal Mail';
$this->supports = [
'shipping-zones'
];
$this->init();
$this->enabled = 'yes';
$this->title = 'Royal Mail 1st Class (Tracked)';
}
/**
*
*/
public function init() : void
{
$this->init_form_fields();
$this->init_settings();
// Save settings in admin if you have any defined
add_action( 'woocommerce_update_options_shipping_' . $this->id, [ $this, 'process_admin_options' ] );
}
/**
*
*/
public function init_form_fields() : void
{
parent::init_form_fields();
}
/**
* #param array $package
*/
public function calculate_shipping($package = [])
{
$rate = array(
'id' => $this->id,
'label' => $this->title,
'cost' => 10
);
$this->add_rate( $rate );
}
}
});
add_filter( 'woocommerce_shipping_methods', function( array $methods ) : array {
$methods['utterly_royal_mail'] = 'Utterly_Royal_Mail_Shipping_Method';
return $methods;
});