For those that encountered issue where, the registration page is not being redirect to the correct page when your site is on multilingual and here is the quick fix to address your issue.
Download the attached 'router.php' and copy this file to folder 'JOOMLA/administrator/components/com_easysocial/includes/'
and overwrite the existing router.php file.
Please backup the original file first before you overwrite with the updated version.
The same fix will be added into next release of EasySocial.
Hope this help and have a nice day