nav2d /StartExploration 2 fails (turtlebot2)

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I'm trying to implement the nav2d autonomous mapping with my turtlebot2 using this tutorial but I am having issues with my navigator node. So far, I am able to run the rosservice call /StartMapping 3 successfully and an initial map is generated. But when I run rosservice call /StartExploration 2, nothing happens and I receive no errors. I even get the message "success: True; message: Send ExploreGoal to Navigator"

Also, the sending a goal manually using the "2D Nav Goal" tool in rviz works.

EDIT: Using the rqt_console while running the services I get "Navigator is now initialized" when I run /StartMapping 3 and when I run /StartExploration 2 it says "Exploration has finished" even though the robot doesn't move at all.

EDIT 2: I ran rostopic echo on the "/Explore/goal" msg when I run /StartExploration and it looks like the Explore node isn't sending any goal to the navigator. The output is:

header: 
   seq: 0
   stamp: 
       secs: 1458916639
       nsecs: 760211716
   frame_id: map
goal_id: 
   stamp: 
       secs: 1458916639
       nsecs: 760217219
   id: /Explore-1-1458916639.760217219
goal: 

 ---

EDIT 3:

Here is the image of the initial map that is created after running /StartMapping 3

Here is my rqt_graph:

rqt_graph

Here is my tf view_frames pdf:

frames.pdf

Here is my customized tutorial3 launch file:

<launch>

    <!-- Some general parameters -->
    <param name="use_sim_time" value="false" />
    <rosparam file="$(find nav2d_tutorials)/param/ros.yaml"/>

    <!-- Start the Operator to control the simulated robot -->
    <node name="Operator" pkg="nav2d_operator" type="operator" >
            <!-- <remap from="scan" to="base_scan"/> -->
            <remap from="cmd_vel" to="mobile_base/commands/velocity"/>
            <rosparam file="$(find nav2d_tutorials)/param/operator.yaml"/>
            <rosparam file="$(find nav2d_tutorials)/param/costmap.yaml" ns="local_map" />
    </node>

    <!-- Start Mapper to genreate map from laser scans -->
    <node name="Mapper" pkg="nav2d_karto" type="mapper">
            <!-- <remap from="scan" to="base_scan"/> -->
            <rosparam file="$(find nav2d_tutorials)/param/mapper.yaml"/>
    </node>

    <!-- Start the Navigator to move the robot autonomously -->
    <node name="Navigator" pkg="nav2d_navigator" type="navigator">
            <rosparam file="$(find nav2d_tutorials)/param/navigator.yaml"/>
    </node>

    <node name="GetMap" pkg="nav2d_navigator" type="get_map_client" />
    <node name="Explore" pkg="nav2d_navigator" type="explore_client" />
    <node name="SetGoal" pkg="nav2d_navigator" type="set_goal_client" >

    </node>

</launch>

And here is my launch file to start up the robot with the laser scanner and minimal.launch:

<launch>
     <include file="$(find turtlebot_bringup)/launch/minimal.launch"/>
             <arg name="custom_param_file" default="$(find turtlebot_navigation)/param/dummy.yaml"/>
     <include file="$(find turtlebot_bringup)/launch/3dsensor.launch">
             <arg name="rgb_processing" value="false" />
             <arg name="depth_registration" value="false" />
             <arg name="depth_processing" value="false" />

     <!-- We must specify an absolute topic name because if not it will be prefixed by "$(arg camera)".
        Probably is a bug in the nodelet manager: https://github.com/ros/nodelet_core/issues/7 -->
             <arg name="scan_topic" value="/scan" />
     </include>

 </launch>

Can anyone help me out?