# Why does the end effector link of my 6 DoF robot act strange when making contact?

Hello,

I'm working with a 6 DoF robot in gazebo. I've been having issues with making the end effector behave properly. When I move it through some boxes for example, it seems to get stuck on the boxes as the rest of the robot continues moving past them. Here's the URDF for link_6 and it's joint. I've tried adjusting some of the world physics properties as well. Any ideas that could be causing this?

<link name="link_6">
<inertial>
<origin
xyz="1.51872095159637 -0.579399630103464 1.1458488535294"
rpy="0 0 0" />
<mass
value="0.01" />
<inertia
ixx="0.00121172108473992"
ixy="-0.000289930478786833"
ixz="0.000101428482694605"
iyy="0.000887798012340719"
iyz="-5.46120722442754E-05"
izz="0.000747466019901337" />
</inertial>
<visual>
<origin
xyz="-0.202 0.165 0.115"
rpy="-1.57 0 0" />
<geometry>
<mesh
filename="package://ms_5_description/meshes/robot_unigripper.STL" />
</geometry>
</visual>
<collision>
<origin
xyz="-0.202 0.165 0.115"
rpy="-1.57 0 0" />
<geometry>
<mesh
filename="package://ms_5_description/meshes/robot_unigripper.STL" />
</geometry>
</collision>
<joint
name="joint_t"
type="revolute">
<origin
xyz="0.0 0.0 0.0"
rpy="0.0 0.0 0.0" />
<parent