Gazebo vacuum gripper not rotating gripped model

edit

Hello all! I'm using the vacuum gripper plug in with the ur5 robot in a similar way to this. Athough I can grip the part and move it around with no problems, I can't rotate it If I rotate just the end effector. You can see the same behavior in the gif of the simulation using the above link. It doesn't make sense if the plug in creates a rigid joint between the model and the end effector. Where could be the problem? TIA!