issue regarding the Pro Site payment receipt notification

I'm having an issue regarding the Pro Site payment receipt notification. As far as I know, it is only one customer. The payment receipt keeps sending duplicate notifications. Between 9:29 PM last night and 7:05 this morning, the subscriber received 11 notifications. I haven't checked if they are still going out but how can I stop them and what is causing this?

I was provided a temporary fix by tech support via chat.