Error Porfolio Filters

hello,

I have the following problem, I installed your plugin for this site:
http://www.tccimmobiliare.ch/

I configured the languages IT, EN and RU.
I translated Pages and Porfolio items.
I also translated the main menu.

The problem is when I switch to the list of objects in the Portfolio (filtered), to understand this is the page in Italian:
http://www.tccimmobiliare.ch/it/filter/affitto/
when i try to see it translated into English (but not work)
http://www.tccimmobiliare.ch/en/filter/for-rent/
(page not found)

But if the url I insert the filter name in Italian it works:
http://www.tccimmobiliare.ch/en/filter/vendita/
In this page the contents are in ENGLISH but the menu item and the URL are in ITALIAN.

How do I solve?

thanks
Alex

https://wordpress.org/plugins/ceceppa-multilingua/