Errors when connecting to Dynamixel motors

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I get the following error the first time I try to launch the launch.

Process[dynamixel_manager-1]: started with pid [2678]
[INFO] [WallTime: 1467413957.109022] pan_tilt_port: Pinging motor IDs 1 through 9...
[FATAL] [WallTime: 1467413957.370123] pan_tilt_port: No motors found.
================================================================================REQUIRED process [dynamixel_manager-1] has died!
process has died [pid 2678, exit code 1, cmd /opt/ros/hydro/lib/dynamixel_controllers/controller_manager.py __name:=dynamixel_manager __log:=/home/armando/.ros/log/1a039064-3fdf-11e6-8fe0-579b9cba6f33/dynamixel_manager-1.log].
log file: /home/armando/.ros/log/1a039064-3fdf-11e6-8fe0-579b9cba6f33/dynamixel_manager-1*.log
Initiating shutdown!
================================================================================
[dynamixel_manager-1] killing on exit

Then I try to launch the launch again and I get the following error

process[dynamixel_manager-1]: started with pid [2493]
[INFO] [WallTime: 1467413913.115092] pan_tilt_port: Pinging motor IDs 1 through 9...
[ERROR] [WallTime: 1467413913.400144] Exception thrown while getting attributes for motor 2 - Invalid response received from motor 2. Wrong packet prefix ['\x00', '\xff']
[ERROR] [WallTime: 1467413913.407137] Exception thrown while getting attributes for motor 2 - Invalid response received from motor 2. Wrong packet prefix ['\x00', '\xff']
[ERROR] [WallTime: 1467413913.412171] Exception thrown while getting attributes for motor 2 - Invalid response received from motor 2. Wrong packet prefix ['\x00', '\xff']
[ERROR] [WallTime: 1467413913.418588] Exception thrown while getting attributes for motor 2 - Invalid response received from motor 2. Wrong packet prefix ['\x00', '\x00']
[ERROR] [WallTime: 1467413913.424202] Exception thrown while getting attributes for motor 2 - Invalid response received from motor 2. Wrong packet prefix ['\x00', '\xff']
[INFO] [WallTime: 1467413913.429494] pan_tilt_port: Found 0 motors , initialization complete.

If it is launching the launcher again, I get randomly one of the errors from the start.

My launch is as follows:

<launch>
    <node name="dynamixel_manager" pkg="dynamixel_controllers" type="controller_manager.py" required="true" output="screen">
        <rosparam>
            namespace: dxl_manager
            serial_ports:
                pan_tilt_port:
                    port_name: "/dev/ttyUSB0"
                    baud_rate: 57142
                    min_motor_id: 1
                    max_motor_id: 9
                    update_rate: 20
        </rosparam>
    </node>
</launch>

I have 5 motors MX-106 and 3 motors MX-28. It has been revised baud_rate (57142) with dynamixel software (ROBOPLUS) in Windows, and not have any ID and I repeated from 1 to 8 ID.

They are using the ROS-HYDRO and :

>rosversion dynamixel_controllers
          0.4.0
>ls -al /dev/USB2DYNAMIXEL
         lrwxrwxrwx 1 root root 7 July 1 17:56 /dev/USB2DYNAMIXEL -> ttyUSB0