Infinite loading during checkout process with Payflow

Question

I have upgraded Magento version from 2.2.1 to 2.2.8, and I was using Braintree as a payment processor for CC payments. Now I enabled Paypal Payflow, but facing an issue.

I am trying placing order through Paypal Payflow Pro(credit card payment method) and I couldn't place the order successfully. However, when I have tried paying through PayPal Express then order got placed successfully. In the case of CC, it is showing endless loading and when I refresh the checkout page, it redirects to the empty cart page. I have checked in the database, the cart is available in the database but the session is getting expired. Anyone have faced this type of issue or anyone know the solution of this issue?

I am using Magento 2.2.8.

There is a discussion on this issue, Infinite loading during the checkout process with payflow. But the solution accepted is not valid in my case, because we can't use a fresh installation at the moment.

I am using Aheadworks onestep checkout extension.