How to release the end effector from leveling. [closed]

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We are currently using a 6-axis robot arm (MyCobot) controlled by MoveIt and with the addition of a gripper. Moveit's automatic route generation cannot sample the valid state of the goal tree if error: RRTConnect: z = 0.15 or less. I want to grab something close to the ground. As you can see in this image, I think one of the factors is that the angle of the 4th axis does not change downward. After investigating, I think that the function to keep the position of the end effector horizontal is working. Is there a way to unlock it and use Move to bring the end effector closer to the ground? We have confirmed that the designated position is a position where the target can be achieved.

pick_and_placer.cpp

#include <ros/ros.h>
#include <moveit/move_group_interface/move_group_interface.h>

int main(int argc, char **argv) {
  ros::init(argc, argv, "pickandplacer");
  ros::NodeHandle nh;

  ros::AsyncSpinner spinner(2);
  spinner.start();

  moveit::planning_interface::MoveGroupInterface arm("mycobot_arm");

  arm.setPoseReferenceFrame("base_link");

  ROS_INFO("Moving to prepare pose");
  geometry_msgs::PoseStamped pose1;
  pose1.header.frame_id = "base_link";
  pose1.pose.position.x = 0.0;
  pose1.pose.position.y = 0.25;
  pose1.pose.position.z = 0.15;


  moveit::planning_interface::MoveItErrorCode ret;

  ROS_INFO("move to WP1");
  arm.setPoseTarget(pose1);
  ret = arm.move();
  if (!ret) {
    ROS_WARN("Fail: %i", ret.val);
    arm.setNamedTarget("vertical");
    arm.move();
  }
  ros::Duration(1.5).sleep();

  ros::shutdown();
  return 0;
}

URDF

<?xml version="1.0" ?>
<robot xmlns:xacro="http://www.ros.org/wiki/xacro" name="firefighter"
       xmlns:controller="http://playerstage.sourceforge.net/gazebo/xmlschema/#controller"
       xmlns:interface="http://playerstage.sourceforge.net/gazebo/xmlschema/#interface"
       xmlns:sensor="http://playerstage.sourceforge.net/gazebo/xmlschema/#sensor">


    <xacro:property name="width" value=".2" />
    <material name="dark blue">
        <color rgba="0.1 0.1 0.9 1" />
    </material>
    <material name="gray">
        <color rgba="0.8 0.8 0.8 1" />
    </material>
    <link name="world"/>



  <link name="base_link"/>
  <joint name="world_to_base_link" type="fixed">
    <parent link="world"/>
    <child link="base_link"/>
    <origin xyz="0 0 0" rpy="0 0 0"/>
  </joint>
   <!-- holder joint & link -->
    <joint name="base_bottom_joint" type="fixed">
        <parent link="base_link" />
        <child link="base_bottom_link" />
        <origin xyz="0 0 0" rpy="0 0 0" />
    </joint>
    <link name="base_bottom_link">
    <inertial>
      <origin xyz="0 0 0" />
        <mass value="3" />
          <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0" />
    </inertial>

        <visual name="base_bottom">
         <origin xyz="0 0 0.01" rpy="0 0 0" />
         <material name="LightGrey">
           <color rgba="0.7 0.7 0.7 1.0"/>
             </material>
          <geometry>
             <box size="0.15 0.15 0.02" />
          </geometry>
        </visual>
        <collision name="base_bottom">
            <origin xyz="0 0 0" rpy="0 0 0" />
            <geometry>
                <box size="0.15 0.15 0.02" />
            </geometry>
        </collision>
    </link>
    <!-- body joint ...