GA enhanced ecommerce session gets lost after redirect

I am tracking checkout process with GTM custom events. All steps gets tracked correctly but checkout flow is broken:

• First checkout event with 'actionField': {'step': 1} is triggered on entering checkout page.
• Second checkout step is triggered after filling form.
• Third checkout step is triggered before redirecting user to payment provider.
• After successful payment user is redirected back to my site where purchase event is triggered (4th column).

Most of payments (17 of 25) was successful but GA shows that 100% abandoned checkout process.

How can I fix that?

The second issue is that in ecommerce referrals I see payment provider in first place. I am pretty sure that this is wrong and it's caused by redirecting users after payment.

You have to set your payment gateway domain (i.e. paypal.com) in Referral Exclusion list, in Property settings.