Old submissions suddenly get resubmitted

old submissions suddenly get resubmitted. For example, today, a submission arrived, one that was already submitted weeks ago!

We will be glad to help you check the issue you are having. May we ask that you provide us the submission ID of the duplicate submissions, please? Could it be that the new submission was really submitted on purpose? I have asked because, normally, a duplicate submission happens when the respondent reloaded the Thank-You page of a form right after the actual submission. When this happens, the duplicate submission will be submitted seconds after the actual submission.

We will wait for your response.