Model sinks and bounces through floor like quicksand-trampoline combination

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I'm new to Gazebo, so this may be a simple mistake. I've uploaded a single model created in Solidworks. At first, the model size was about 1000x larger than it was meant to be, probably because millimeters were interpreted as meters. However, the model would fall right through the ground plane immediately. After I changed the scale to make it 1000x smaller, and added collision, the model would then fall to the floor at a normal rate and began to sink at a slower rate, like quicksand. After some more adjustments, the model still sinks through the floor but then bounces back up, as if this "quicksand" has elastic properties. Note that the real time factor is running at around 0.03 most of the time. I honestly have no idea how to fix this. Here's my .world file:

<sdf version="1.4"> <world name="default">

<include>
  <uri>model://ground_plane</uri>
</include>
<include>
  <uri>model://sun</uri>
</include>
<model name="my_mesh">
  <pose>0 0 1  1.57 0 1.57</pose>
  <static>false</static>
  <link name="body">
<collision name="collision">
    <pose>0 0 1  1.57 0 1.57</pose>
    <geometry>
    <mesh>
      <uri>file://BenpedalMesh1.dae</uri>
    <scale>0.001 0.001 0.001</scale>
    </mesh>
  </geometry>
</collision>
    <visual name="visual">
      <geometry>
        <mesh>
    <uri>file://BenpedalMesh1.dae</uri>
    <scale>0.001 0.001 0.001</scale>
    </mesh>
      </geometry>
    </visual>
  </link>
</model>

</world> </sdf>