Image transform not working with different locales
Ran into a similar problem on a past project, it could be your .htaccess acting up and redirecting the call to cpresources to /benl/cpresources as opposed to /cpresources/.

If you look at your console on the page that the image is broken - you might be getting a 404 error. If that is the case...

Adding this rewrite rule helped my project and may help yours as well.

    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteRule ^cpresources/transforms/(.*)  /cpresources/transforms/$1 [L,R,NE,QSA]


Add this rule to your .htaccess in your /benl/ directory before the default index.php rewrite.