PayPal Express Checkout Issue Magento 2

Job ID: 31406159

Budget: £20 – £250 GBP

We recently swapped from Magento1 to Magento2 (around 10 days ago)

Using PayPal Payments Hosted Pro solution

Discovered a bug where PayPal is crashing mid processing on Express checkout. (See screenshot)

Server company are not sure what the issue is and along with PayPal, are asking me to speak to a developer.

Debit and credit card payments all working ok.
Also works as a standard PayPal checkout ok but then does not then go to the success page. Bounces to the home page with error 'Invalid Form Key - Please Refresh The Page'

Also getting error - IPN (instant payment notifications) PayPal said the issues are connected.
They said....
Please check your server that handles PayPal Instant Payment Notifications (IPN). IPNs sent to the following URL(s) failed:

Only want Magento 2 developer please.
Related categories: PHP Magento eCommerce PayPal API HTML