Error Message on submit

Hi
I have set up the form at http://www.scratchnscuffsaway.co.uk/wp/?page_id=69 and it works fine, sends the email fine plus a BCC and includes the attachment.
My only problems is once you hit the submit button then I get a Page not found error and its trying to find the following address …. http://www.scratchnscuffsaway.co.uk/wp/?page_id=69#FSContact1
I had a web address redirect within the form settings but its not even showing a confirmation of the email sent let alone redirecting ot the page I’ve requested. What am I doing wrong as essentially its doing its job and the quotations are being sent but it looks terrible when after you fill the form out it shows a page not found error!?!

Thanks (first time using this contact form plug in!)

https://ww.wp.xz.cn/plugins/si-contact-form/