CKEDITOR + KCFINDER with INDEX.PHP removed

I have developed an application using CI3, CKEDITOR 4.4, KCFINDER version 2.51
I have removed the index.php in the URL by using .htaccess
The editor part works perfectly but I can't get KCFINDER browse function to work with images or files server


Click on browse calls http://mysite/assets/kcfinder/browse.php...angCode=fr
This results in error 404 page not found

My htaccess is
#   Active URL rewrite
    RewriteEngine On
    RewriteBase /

#   do not rewrite for following path
#    RewriteCond %{REQUEST_URI} !^/assets/kcfinder/
#   All URL's below are not rewritten
    RewriteCond $1 !^(index\.php|.*\.css|.*\.js|.*\.jpg|.*\.JPG|.*\.gif|.*\.png|.*\.pdf|browse\.php|robots\.txt|.*\.txt)
#   All other are directed to index.php.
    RewriteRule ^(.*)$ index.php/$1 [L]

I AM PRETTY SURE THAT MY PROBLEM COMES FROM THE URL REWRITE THAT CHANGES THE http://mysite/assets/kcfinder/browse.php
BUT I DON'T FIND OUT HOW TO AVOID IT
If I uncomment RewriteCond %{REQUEST_URI} !^/assets/kcfinder/ call to the browser display contents of browser.php as text !

Hope someone can help
Thanks