problem with redirect after form

Dear support,

I followed the instruction found here: https://kriesi.at/support/topic/contact-form-redirection/
The redirect was working smoothly but now it is not working anymore for some pages.

For instance in the homepage contact-form the redirect works well: http://www.inspirationgroup.it/
but it stopped working on my landing page: http://www.inspirationgroup.it/compra-un-appartamento-a-berlino/

Can you please help me out?

Thanks!