Magento 2.2 - Checkout Fix - success page not showing

I'm struggeling with the Magento checkout page not showing issue since a few days and I'm looking for someone who has sufficient knowledge in Magento 2 to fix Magento "success page not showing" after successful order. We are using Magento 2.2.2 with the latest Stripe-official v2.0.10 payment module with a one-page-checkout layout from firecheckout extension. To describe the issue a little further, we have tested the checkout previously with braintree payment which worked as expected (success page showing after successful order), but we have switched to Stripe module after some management decisions, where after successful order, the site loads or goes back to the homepage immediately instead of showing a success page. Another way to see it is that the success page actually exist under "~/checkout/onepage/success", but somehow either the payment module or the checkout controller doesn't link to it (checkout/onepage/success) and instead goes back to the homepage after successful order. Please also note that we have a Multistore setup with subdirectories in a Nginx fpm environment such as [login to view URL] etc. Meaning that the success page ideally should show not only in [login to view URL]"en"/checkout/onepage/success but also in [login to view URL]"us"/checkout/onepage/success etc. And finally please also note that we are offering this task for 80-240HKD and not USD. Please do respond if this issue sounds familiar to you and please kindly DO NOT respond if you expect to manage this task for 200USD which we somehow have NOT posted this way.