It seems the combination of two plugins is the result for this behavior. But still I am waiting a reply since days for the mess with menus and polylang in another thread.
Hello.
I kindly ask you to give me a reply. I need to make the translations of the menus.
I contacted Polylang and they say it is a conflict with the theme.
I did not add or change ANYTHING special on your theme, I did not add CSS to menu.