HITL: rudder moves right only

PX4 Autopilot
1

I designed a new FW model in sitl_gazebo. The mixer file I created looks as follows

Aileron mixer (roll)
---------------------------------
M: 1
S: 0 0  -10000  -10000      0 -10000  10000
M: 1
S: 0 0  -10000  -10000      0 -10000  10000

Elevator mixer
------------
M: 1
S: 0 1  10000  10000      0 -10000  10000

Motor speed mixer
------------
M: 1
S: 0 2      0  20000 -10000 -10000  10000

Rudder mixer
-----------------
M: 1
S: 0 3  10000  10000      0 -10000  10000

and the corresponding sdf control channels are

<control_channels>
        <channel name="left_elevon">
          <input_index>0</input_index>
          <input_offset>0</input_offset>
          <input_scaling>-1</input_scaling>
          <zero_position_disarmed>0</zero_position_disarmed>
          <zero_position_armed>0</zero_position_armed>
          <joint_control_type>position_kinematic</joint_control_type>
          <joint_name>left_elevon_joint</joint_name>
        </channel>

        <channel name="right_elevon">
          <input_index>1</input_index>
          <input_offset>0</input_offset>
          <input_scaling>1</input_scaling>
          <zero_position_disarmed>0</zero_position_disarmed>
          <zero_position_armed>0</zero_position_armed>
          <joint_control_type>position_kinematic</joint_control_type>
          <joint_name>right_elevon_joint</joint_name>
        </channel>

        <channel name="elevator">
          <input_index>2</input_index>
          <input_offset>0</input_offset>
          <input_scaling>-1</input_scaling>
          <zero_position_disarmed>0</zero_position_disarmed>
          <zero_position_armed>0</zero_position_armed>
          <joint_control_type>position_kinematic</joint_control_type>
          <joint_name>elevator_joint</joint_name>
        </channel>

        <channel name="rudder">
          <input_index>3</input_index>
          <input_offset>0</input_offset>
          <input_scaling>1</input_scaling>
          <zero_position_disarmed>0</zero_position_disarmed>
          <zero_position_armed>0</zero_position_armed>
          <joint_control_type>position_kinematic</joint_control_type>
          <joint_name>rudder_joint</joint_name>
        </channel>

        <channel name="rotor4">
          <input_index>4</input_index>
          <input_offset>0</input_offset>
          <input_scaling>-3500</input_scaling>
          <zero_position_disarmed>0</zero_position_disarmed>
          <zero_position_armed>0</zero_position_armed>
          <joint_control_type>velocity</joint_control_type>
          <joint_name>rotor_puller_joint</joint_name>
        </channel>
</control_channels>

The problem is that the rudder (yaw channel) moves to the right hand side only. If I turn the RC transmitter joggle to the left, then the rudder stays at zero position. It seems that the signal from the yaw channel is limited somewhere between [0, 1], but should be [-1, 1]. Probably, these limitations are defined in a config I should change.

I use x4 of the version 1.12.3.

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