I found the error:
<joint type="revolute" name="left_ankle_hinge">
<physics>
<ode>
<provide_feedback>true</provide_feedback>
</ode>
</physics>
<pose>0 0 0.04 0 0 0</pose>
<child>left_foot</child>
<parent>leftlower_leg</parent>
<axis>
<xyz>1 0 0</xyz>
</axis>
</joint>
should be changed to:
<joint type="revolute" name="left_ankle_hinge">
<physics>
<provide_feedback>true</provide_feedback>
</physics>
<pose>0 0 0.04 0 0 0</pose>
<child>left_foot</child>
<parent>leftlower_leg</parent>
<axis>
<xyz>1 0 0</xyz>
</axis>
</joint>