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Why does my custom collada mesh makes the turtlebot wheels twist?

Hi all,

my custom collada mesh does strange things to the turtlebot model.

My goal is to make a simulation environment of our department. So I created a model of the walls and doors of our department with SketchUp 2016 and exported the model to the Collada format (.dae). Next step was to create a SDF formatted world, with the department model included. This is my world file:

<?xml version="1.0" ?>
<sdf version="1.4">
  <world name="default">
    <!-- Initial Camera Position -->
    <gui>
      <camera name=camera_default>
        <pose>
          -4.0 2.0 8.0 0.0 0.7 0.0
        </pose>
      </camera>
    </gui>
    <!--
    <include>
      <uri>model://ground_plane</uri>
    </include>
    -->
    <!-- A global light source -->
    <include>
      <uri>model://sun</uri>
    </include>
    <!-- Own physics settings to speed up simulation -->
    <physics type='ode'>
      <max_step_size>0.01</max_step_size>
      <real_time_factor>1</real_time_factor>
      <real_time_update_rate>100</real_time_update_rate>
      <gravity>0 0 -9.8</gravity>
    </physics>
    <model name="department">
      <static>true</static>
      <link name="link">
        <pose>0 0 0 0 0 0</pose>
        <collision name="coll">
          <geometry>
            <mesh>
              <uri>model://floorplan.dae</uri>
            </mesh>
          </geometry>
        </collision>
        <visual name="visual">
          <geometry>
            <mesh>
              <uri>model://floorplan.dae</uri>
            </mesh>
          </geometry>
        </visual>
      </link>
    </model>
  </world>
</sdf>

When I now spawn this world in Gazebo 7.0.0 together with a TurtleBot in it, the active wheels of the TurtleBot are twisting around the driving direction, making the TurtleBot hopping and floating ~5-10cm above the floor of the department model.

When I spawn the same TurtleBot model with just ground plane (as commented in the world file above), everything is fine.

So my guess is that something is wrong with my collada model. The model can be downloaded here: https://github.com/StephanOpfer/turtlebot/blob/kinetic/turtlebot_bringup/world/floorplan.dae

Maybe you have some tips for exporting or validating the collada file, or you can approve that you can see the same behavior as I do? For the latter you probably only have to checkout the repo https://github.com/StephanOpfer/turtlebot/blob/kinetic/turtlebot_bringup compile it. Then you copy the floorplan.dae into ~/.gazebo/models and run

roslaunch turtlebot_bringup simulation.launch

Greetings, Stephan