CTF7 Sending forms twice

I’ve build many forms on one site using CTF7 plugin. Everything is working fine – except that the forms are being received twice.

Unlikely the people filling the form in are clicking submit twice as its happening with EVERY form submitted (20 + a day). As you can image, my client is rather annoyed by this.

I’ve googled it, but can’t come up with a solution. All the forms have :
on_sent_ok: “location = ‘http://www.mywebsite.com/request-submitted/’;” added to the additional settings box.

My theme is DIVI by elegant themes.
The websites this is happening on are: http://www.pension-bridging.co.za/
and http://pensionbridging.co.za/web/

Any help would be greatly appreciated!