Best for SEO but some important problems

We needed the best language plugin for SEO for one of our sites dedicated to SEO.
No doubt that yours is the best because of the links editing!
The problem is that the plugin starts to redirect our main page to the sublanguage(we test it in Google and in other platforms).After desactivation of the plugin we have got worst problems-all pages start to redirect only to the main one.We should add special scripts to the wp XMLRPC.PHP file and to setup again the permalinks.