Repeat Form Submission Glitch

I run a website building business, and one form that a client submitted on February 2nd has duplicated itself 8 times, sporadically.  I have attached a screenshot below.  It is the same exact information, and it shows up in my submissions, and sends me notifications of the form as if it is a brand new submission.

My client is an experienced user with jotform, and has over a dozen projects with me through jotform.  But this one in particular, keeps resubmitting itself over the last two months for whatever reason.   Please advise.

It is for Bullsbrook Water Delivery Service from Don Green

If that is the only occurrence, I can assume that a user has reloaded the Thank You page several times. It will process another submission with same information entered. I can suggest to add captcha to the form to prevent issues like this: How-to-Add-a-Captcha-Field

Also, you can consider limiting submissions on a form:

How-to-Set-Unique-Submissions-on-a-Form