Here’s a typical example of how you might experience a problem with form duplicates.
It’s Friday afternoon at the end of the semester. You send email to your students reminding them to submit student satisfaction form. Some may have done so and do not remember if they have submitted the form. So they submit the form for the second time.
Email notifications come in. You think, “Great, they have submitted the forms.” But when you look at the submitted forms, you realize you have received the submission twice from some students!