[Plugin: FormBuilder] You have already submitted this form data once

I just installed the last Form Builder plugin and it works great.

My only problem is that when I submit the form with validation problems (to test), the system lists all the problems (good) but also display the message:

“You have already submitted this form data once.”

I change the title and submit again and it works, but I don’t want this problem to happen with the final users, which won’t understand that they need to change the title.

Any idea? Something wrong I did?
I might have refresh the page in the process, but as the fields weren’t valid, the form shouldn’t have been submitted.

Thanks!

Johanna