Adding links on Iris model in gazebo makes hovering unstable

Hi, I’m trying to attach some sensors on Iris.
To do that, I added a small box link because I need a joint between th iris base link.
However after that, px4 can’t hover regardless of the weight of the added link. Below is added part of sdf source code.

<!--add-->
<link name = "front_camera">
  <inertial>
    <mass>0.159</mass>
  </inertial>
  <pose frame=''>0.1 0 -0.05 0 0 0</pose>
  <visual name = "front_camera_visual">
    <geometry>
      <box>
        <size>0.033 0.175 0.03</size>
      </box>
    </geometry>
  </visual>
  <sensor name='front_stereo_camera' type='multicamera'>
    <update_rate>60.0</update_rate>
    <camera name = "left">
      <pose>0 0.06 -0.1 0 0 0</pose>
      <image>
        <width>1200</width>
        <height>360</height>
        <format>R8G8B8</format>
      </image>
      <noise>
        <type>gaussian</type>
        <mean>0.0</mean>
        <stddev>0.007</stddev>
      </noise>
    </camera>
    <camera name = "right">
      <pose>0 -0.06 -0.1 0 0 0</pose>
      <image>
        <width>1200</width>
        <height>360</height>
        <format>R8G8B8</format>
      </image>
      <noise>
        <type>gaussian</type>
        <mean>0.0</mean>
        <stddev>0.003</stddev>
      </noise>
    </camera>
    <plugin name="front_camera_controller" filename="libgazebo_ros_multicamera.so">
      <alwaysOn>true</alwaysOn>
      <updateRate>0.0</updateRate>
      <cameraName>front_stereo_camera</cameraName>
      <imageTopicName>image_raw</imageTopicName>
      <cameraInfoTopicName>camera_info</cameraInfoTopicName>
      <frameName>left_camera</frameName>
      <rightFrameName>right_camera</rightFrameName>
      <hackBaseline>0.12</hackBaseline>
    </plugin>
  </sensor>
</link>
<joint name = "front_camera_joint_pitch" type = "revolute">
  <child>front_camera</child>
  <parent>base_link</parent>
  <axis>
    <xyz>0 1 0</xyz>
    <dynamics>
      <damping>0</damping>
      <friction>0</friction>
    </dynamics>
    <use_parent_model_frame>1</use_parent_model_frame>
  </axis>
</joint>
<!--add-->

I’m not sure what’s wrong with your model above, but did you compare with other examples in the repository?
For example here’s an iris with rplidar. https://github.com/PX4/sitl_gazebo/blob/master/models/iris_rplidar/iris_rplidar.sdf