We hit what looks like a bug in implementation of get_model_state service in Gazebo. The scenario that we are working with is the following: imagine an object and a robot that is always oriented towards this objects and is certain distance away from it. We expect the object's position in robot's coordinate frame to be, let's say, 40cm away on x axis and 0 cm on y axis. Now if we rotate both the robot and the object by 180 degrees, we would expect that relative position would stay the same since robot is still looking straight at an object and it didn't move anywhere in relation to the object, but gazebo gives us -40cm on x axis and 0 on y axis. These numbers get weirder with different yaw angles of the robot with respect to the world coordinate frame. So it looks like the absolute location in the world still matters when getting the relative pose of one objects in some other coordinate frame (except 'world'). Is there something obvious that I am missing here?