We've been tracking this issue for a while. The "Rolled back transaction" error is caused by changes to guest checkout processing that Magento made in 2.2.4, which causes an error when certain things during order processing don't work correctly (such as getting an error when adding a new card).
We believe this to be a problem in the Magento core. Unfortunately there are not any changes we could make to fix or avoid this problem as a third party. We expect the same bug will affect any other solution that triggers an exception and SQL rollback during order placement.
The error handling can be fixed/improved so that the customer sees the real error, by reverting the new transaction code in Magento's 'GuestPaymentInformationManagement' class. But that means modifying the Magento core, which is not a proper solution by any means.
There is a Magento bug report tracking the issue here: https://github.com/magento/magento2/issues/18752
Magento acknowledged the issue, but as of yet has not provided any further guidance.
Was this article helpful?
That’s Great!
Thank you for your feedback
Sorry! We couldn't be helpful
Thank you for your feedback
Feedback sent
We appreciate your effort and will try to fix the article