Wp Admin Bar Customizing Labels

Don’t use add_filter with the_content that way; that is meant for a different context – when you are filtering a returned WP post object.

Try something like this instead:

function replace_customer_area_title( $wp_admin_bar ) {
    $newtitle = __('Custom Title', 'cuar');
    $wp_admin_bar->add_node( array( 'id' => 'customer-area', 'title' => $newtitle, ) );
}

add_filter( 'admin_bar_menu', 'replace_customer_area_title' , 33 ); 

add_node should modify an existing node, if found.

This must run after the original node was added with priority of 32, so we have used 33 here as an example.