Hi Stephen,
Thanks for reaching out to us about this.
We are aware of this problem when collecting attendee information and we are currently working towards a new re-design of how this functionality works, so that it prevents required attendee information missing in situations like you mention.
We don’t have a date for when this will be available but it will likely be in one of our future feature releases of our plugins.
In the meantime, the only workaround for this problem is to notify the users about the missing information so they can fill it themselves using their account and navigating to the My Tickets page that should have a URL like yoursite.com/event/event-slug/tickets
I know that is not ideal, but it will at least allow you to fill in the information after the ticket purchase.
I hope that helps. Let us know if any follow up questions.
Best,
Victor