I have one example. In profil_activate.php file, find line:
$aTemplate = $rEmailTemplate -> getTemplate( 't_Activation') ;
You should replace it by:
$aTemplate = $rEmailTemplate -> getTemplate( 't_Activation', $p_arr['ID']) ;
Otherwise default language email is sent. For example if profil has joined in english and default language is french, email is sent in french. But profil is in english, it's very confusing!
You should fix all lines that miss this parameter. I have to do this manually each upgrade :(
Thanks!