After installing sh404sef on a site using joomfish for dual language website the homepage would not change back to english when I clicked on the translation flag.
I fixed this by editing the sh404 sef urls:
Go to Components > SH404SEF > URL manager > New:
New SEF URL: en
non-SEF Url: index.php?lang=en
It should work now.
PS. If you don’t know what the non-SEF Url is, then disable sh404sef and set the joomla seo setting in the joomla control panel to No.
Go to front end and click on the homepage and click on the language links to go to another language and then back t english. You will see the url in the address bar.