I am using CiviCRM 5.13.4 on Drupal 7.67.
I have built a Webform that captures Contact Details, a Membership of our organisation, and Payment (using a Contribution) for that Membership. I have also enabled the 'Preview Page' function of the Webform. This ends up taking the user through the page that captures personal details, the page that takes the payment, and finally the page that previews and submits the details. The problem is that if one returns from the preview to change a detail one is asked for a second payment, and if one abandons the transaction on the preview page the payment has still been taken, with no membership recorded.
Surely the preview and confirmation of details should come before the payment? Is there a way of configuring this, or is it a bug?