Ninja Forms failure closes popup

I use Ninja Forms with Popup Maker. We need the popup to close when clicking on the background, but with this option enabled, the popup also automatically closes when clicking the submit button.

This is fine when the submit is successful, as we can trigger the popup to open again on form send. But when there is an error (e.g. customer did not agree to privacy disclaimer) the popup closes without the customer ever seeing the error message, that the form did not send.

How can I show the customer an error message in the popup on a failed Ninja Form submit?