Wrong return_url in multisite setup when using subdomains with place order button

[darkopetreski]

Describe the Bug

I am using a subdomain for the wordpress, domain.com/shop.
Due GDPR and requiremens of the client I am disabling the smart button and use the paypal redirect, with the following code as described here https://github.com/woocommerce/woocommerce-paypal-payments/wiki/Actions-and-Filters#disable-checkout-smart-buttons

add_filter('woocommerce_paypal_payments_use_place_order_button', '__return_true');
add_filter('woocommerce_paypal_payments_place_order_button_text', function() {
    return __( 'Place order', 'woocommerce' );
});

When the user pays the order a redirect is made back to the shop. But the redirect is wrong.

To Reproduce

1. Setup the wodrepss as subdomain, domain.com/shop
2. Add the code from above to functions.php
3. Add item to cart and go to the cart
4. Click the button to pay the order
5. Pay the order with paypal
6. The return url is wrong, /shop/shop?...

Screenshots

Expected Behavior

The return url should be domain.com/shop?....

Actual Behavior

The return url is: domain.com/shop/shop?....

Environment

• WordPress Version 6.2.2
• WooCommerce Version 9.3.1
• Plugin Version 2.9.0
• Browser and Version Any browser
• Any other plugins installed

Additional info

There is a fix for a similar bug here #2157