How to stop a custom form from being submitted twice simultaneously

We have an issue with a custom form’s validation/submit steps being processed twice, resulting in unexpected behavior. This form creates an object with some unique fields, therefore, when the second process gets ran, its erring with duplication errors. Essentially, the first process ran successfully, but since the second process took over the routing, the user gets a duplication error instead of being redirected to where they should be after a successful submission.

Is there a way to disable a form submission process if one is already active?