The loop_rate() for my node doesn't change the publish frequency

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Hi to all,

I'm having problems with the loop_rate() function for my node. I set it at 10hz and then I publish some topics in the while() loop but when I rostopic them, I see that they are published only at 4 hertz! What am I doing wrong?

This is my code:

 #include "ros/ros.h"
#include "std_msgs/String.h"
#include "geometry_msgs/Twist.h"
#include <unistd.h>

#include <sstream>
#include <iostream>
#include <stdio.h>
#include <string.h>

#include "../include/robo_base/RoboteqDevice.h"
#include "../include/robo_base/ErrorCodes.h"
#include "../include/robo_base/Constants.h"
#include "robo_explorer/robo_io.h"

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

  std::string port = "";

  ...  

  n.getParam("/robo_explorer/port", port);
  n.getParam("/robo_explorer/sys", sys);
  n.getParam("/robo_explorer/board", riox_board);
  n.getParam("/robo_explorer/enc", enc);
  n.getParam("/robo_explorer/io", io);
  n.getParam("/robo_explorer/imu", imu);
  n.getParam("/robo_explorer/velocity", velocity);
  n.getParam("/robo_explorer/rate", rate);


  ros::Publisher sys_pub = n.advertise<std_msgs::String>("robo_explorer/sys", 1);
  ros::Publisher enc_pub = n.advertise<std_msgs::String>("robo_explorer/enc", 1);
  ros::Publisher vel_pub = n.advertise<std_msgs::String>("robo_explorer/velocity", 1);
  ros::Publisher io_pub = n.advertise<std_msgs::String>("robo_explorer/io", 1);
  ros::Publisher imu_pub = n.advertise<std_msgs::String>("robo_explorer/imu", 1);

  ros::Subscriber cmd_sub = n.subscribe("/robo_explorer/cmd_vel", 1, &RoboteqDevice::cmdCallback, &device);
  ros::Subscriber cmd_io = n.subscribe("/robo_explorer/io_status", 1, &RoboteqDevice::cmd_ioCallback, &device);

  double current_time =ros::Time::now().toSec();
  double last_time =ros::Time::now().toSec();


  ros::Rate loop_rate(rate);
  while (ros::ok())
  {


    //System Topic
    if (sys == 1){
    .....
  sys_pub.publish(msg_sys);

  }


    //Encoder Topic
    if (enc == 1){
vel_pub.publish(msg_vel);
enc_pub.publish(msg_enc);
...
    }


   //IO Topic
   if (io == 1){
     ...
io_pub.publish(msg_io);
    }

   if (imu == 1){
..
imu_pub.publish(msg_imu);

    }

    ros::spinOnce();

    loop_rate.sleep();
    ++count;
  }

  return 0;
}

These are all the published topics:

/robo_explorer/cmd_vel
/robo_explorer/enc
/robo_explorer/imu
/robo_explorer/io
/robo_explorer/io_status
/robo_explorer/sys
/robo_explorer/velocity

and for example this is one of the output:

rostopic echo /robo_explorer/io

data: "1612553682.755857579,0,0,0,0,0,0,0,0,0,0,0,0,100"
---
data: "1612553683.020352972,0,0,0,0,0,0,0,0,0,0,0,0,101"
---
data: "1612553683.285076521,0,0,0,0,0,0,0,0,0,0,0,0,102"
---
data: "1612553683.551031712,0,0,0,0,0,0,0,0,0,0,0,0,103"
---
data: "1612553683.816192936,0,0,0,0,0,0,0,0,0,0,0,0,104"
---
data: "1612553684.082027678,0,0,0,0,0,0,0,0,0,0,0,0,105"
---
data: "1612553684.347815952,0,0,0,0,0,0,0,0,0,0,0,0,106"
---
data: "1612553684.613140284,0,0,0,0,0,0,0,0,0,0,0,0,107"
---
data: "1612553684.878549824,0,0,0,0,0,0,0,0,0,0,0,0,108"
---
data: "1612553685.144171685,0,0,0,0,0,0,0,0,0,0,0,0,109"

as you can see, there are only 4 samples for each second. How can I solve this?

P.S. this is the output for the hz:

rostopic ...