Mulitiple Submissions on a form

Has anyone experience cases where there were multiple duplicate submissions?

We have not received cases of multiple submissions however it could be possible in rare scenarios. This may happen if the user submits a form and then goes back and submit again. That could trigger multiple submissions. 

You can enable Unique submission settings to avoid the duplicate submissions. Here is the article that explains this process - How-to-Set-Unique-Submissions-on-a-Form 

I hope this helps.