Zend certified PHP/Magento developer

Magento 2.3: Klarna + Coupon Code results in “main.ERROR:Order line totals do not total order_amount”

Klarna Payment method is activated in the checkout. It works fine as long as you don’t use a coupon code. If you do, the checkout page breaks with the following error:

main.ERROR:Order line totals do not total order_amount – 530 != 490

Here is what I did already:

  • Deactivated ALL third party modules
  • Activated Luma Standard Theme
  • Deactivated all other payment methods
  • Went through the database in the hope to find anything
  • Tested different tax and pricing settings
  • Updated from 2.3.3 to 2.3.4

Does anybody have an idea what I could have missed?
Or what I should test next?

Using Magento 2.3.3 (live) and 2.3.4 (dev). Happens on both instances. Live and Dev are located on different servers.