Why does this rosserial arduino code only permits a single subscriber?

edit

Hi, I have a simple arduino code that takes in inputs from my joystick where a button on my joystick would act as a switch ( pressing once will turn 'on' and pressing it again turns it 'off'). My code basically publish the output as true or false and it works. However the problem arises when I add another subscriber to the cmd_vel topic. My output doesn't change and later a lost sync error occurs.

#include <ros.h>
#include <std_msgs/Float32.h>
#include <sensor_msgs/Joy.h>
#include <std_msgs/String.h>
#include <geometry_msgs/Twist.h>
#include <std_msgs/Bool.h>
ros::NodeHandle nh;

float tempx;
float tempz;
float joy_button;
boolean last_reading;
boolean currentReading;
boolean flag;
boolean published;

void overrideCallback(const sensor_msgs::Joy& joy_msg){
  joy_button = joy_msg.buttons[4];
}

/*
void joyCallback(const geometry_msgs::Twist& cmd_msg){

    tempx = cmd_msg.linear.x;
    tempz = cmd_msg.angular.z;
}*/

//ros::Subscriber<geometry_msgs::Twist> joy_sub("cmd_vel", &joyCallback );
ros::Subscriber<sensor_msgs::Joy> override_sub("joy", &overrideCallback);

std_msgs::Float32 override_msg;
ros::Publisher override_pub("override_status", &override_msg);

std_msgs::Bool pushed_msg;
ros::Publisher pub_button("pushed", &pushed_msg);



void setup(){
  nh.initNode();
  nh.subscribe(override_sub);
  //nh.subscribe(joy_sub);
  nh.advertise(override_pub);
  nh.advertise(pub_button);
  last_reading = false;
  currentReading = false;
  flag=true;
}


void loop(){
  override_msg.data = joy_button;

  if (override_msg.data == 0.0){
    currentReading = false;
  }else currentReading = true;

  if (currentReading && !last_reading) {
    flag=!flag;
    if (flag) {
      published = true;
    }
    else {
      published = false;
    }
  }


  last_reading = currentReading;
  pushed_msg.data = published;
  pub_button.publish(&pushed_msg);  
  override_pub.publish(&override_msg);
  nh.spinOnce();
  delay(5);
}

The above code works without the commented lines. Any help would be appreciated. Thank you.