Pending (Incomplete Transaction) when user missed a required field on membership/contribution
I have a form where users purchase a membership with a contribution. We use Authorize.net to process payments.
I noticed that when users fill out the form correctly the first time, everything is fine.
But if the user misses a required field, clicks submit, sees the error message, corrects the mistake, and submits again, their contribution is stuck as "pending (incomplete transaction)" even though they have confirmed their payment on the confirmation page. No transaction is sent to Authorize.net in this case.
What is the difference between data sent when no required fields are missed and when required fields are not missed?