Some customers are redirected to the cart page after successfully finishing an order

[viniciusfabri]

Hi,

We are noticing an odd behaviour on Production: ~20% of customers never see the success page, but rather are redirected to the cart page after finishing payment. This happens because the EMS module is not being able to load up data from the session here: https://github.com/emspay/magento2/blob/master/app/code/EMS/Pay/Controller/EmsAbstract.php#L73

We are not able to reproduce this issue ourselves, but we placed some logs on those functions in Production, and the line above returns null/empty

The redirect flow is as follows:

• EMS redirects to /emspay/success
• It's not able to load the order, but it still redirects to /checkout/onepage/success
• The validator in this page isn't able to load the order, so it redirects the user to /checkout/cart

We are using Redis for session management. My question is if you faced this before on other customers/projects, and if so, how it was resolved.