Sub menu item not found by system
Found a way to display the menu correctly.

{% import _self as menus %}

&lt;ul class="nav side-menu"&gt;

{% for item in items %}

{% if not item.below %}
  &lt;li {% if item.in_active_trail%}class="current-page"{% endif %}&gt;
    {{link(item.title, item.url)}}
    &lt;/li&gt;
{% else %}
  &lt;li&gt;&lt;a&gt;&lt;i class="fa fa-edit"&gt;&lt;/i&gt; {{item.title}} &lt;span class="fa fa-chevron-down"&gt;&lt;/span&gt;&lt;/a&gt;
    &lt;ul class="nav child_menu"&gt;

      {% for subItem in item.below %}
        &lt;li&gt;&lt;a href="{{ path(subItem.url.routename, {(subItem.url.routeParameters|keys|first) : (subItem.url.routeParameters|first)}) }}"&gt;{{subItem.title}}&lt;/a&gt;&lt;/li&gt;
      {% endfor %}
    &lt;/ul&gt;

{% endif %}

{% endfor %}
&lt;/ul&gt;