Restrict authors to seeing ONLY their media files

I’d like to restrict authors ability to see files uploaded by other users because this causes no end of trouble, since they can change captions etc.

I tried this code from here How to hide media uploads by other users in the Media menu?

add_action('pre_get_posts','users_own_attachments');
function users_own_attachments( $wp_query_obj ) {

    global $current_user, $pagenow;

    if( !is_a( $current_user, 'WP_User') )
        return;

    if( 'upload.php' != $pagenow )
        return;

    if( !current_user_can('delete_pages') )
        $wp_query_obj->set('author', $current_user->id );

    return;
}   

This only works on the media screen, not when you select a file on a post to actually upload.

I also tried the second solution, but it’s causing issues with my autocomplete search function and I can’t figure out why.

Is there a way to stop authors seeing others files when they’re making a post?