POST request Stops after a short time of operation about esp8266-iot-framework HOT 9 CLOSED

// My code
#include <Arduino.h>
#include "WiFiManager.h"
#include "webServer.h"
#include "updater.h"
#include "fetch.h"
#include "configManager.h"
#include "timeSync.h"
#include <SoftwareSerial.h>
#include <ArduinoJson.h>
#include <PubSubClient.h>
#include <ESP8266httpUpdate.h>
#include "LittleFS.h"
int rxPin = D6;
int txPin = D5;

SoftwareSerial linkSerial(rxPin, txPin);

const char *API = "pls put your api to test";
//String bodyPayload = "{\"id\": 199087, \"name\": \"kelvin\", \"usage\":121.40, \"balance\":144.90}";

char JSONmessageBuffer[1000];
char jsonData[500];
const int blueLed = D4; // multitasking led
int ledOpState = LOW;   //publish data operation led

/*** Serial LED states for software data sent ***/
bool serialState = false;
unsigned long prevSerialTime = 0;
unsigned long prevSerialTime2 = 0;
unsigned long resetTimePrev = 0;

struct taskPost
{
  unsigned long ratePost;
  unsigned long previousPost;
};

/*struct taskGet
{
  unsigned long rateGet;
  unsigned long previousGet;
};*/

taskPost taskA = {.ratePost = 10000, .previousPost = 0};
//taskGet taskB = {.rateGet = 20000, .previousGet = 0};

void setup()
{
  // put your setup code here, to run once:
  delay(15000);
  Serial.begin(115200);
  while (!Serial)
    continue;
  linkSerial.begin(9600);
  //delay(1500);
  delay(1000);
  delay(1000);
  delay(2000);
  LittleFS.begin();
  GUI.begin();
  configManager.begin();
  WiFiManager.begin("ESP_AP");
  timeSync.begin();
  pinMode(blueLed, OUTPUT);
}

/******* Software Serial data transfer(uno-ESP8266) led blink function ****/
void serialData()
{
  if (millis() - prevSerialTime >= 60000)
  { //turn off delay (blue led) is 1 min
    digitalWrite(blueLed, HIGH);
    serialState = false;
    prevSerialTime = millis();
  }

  if (serialState == false)
  {
    if (millis() - prevSerialTime2 >= 3000)
    {
      digitalWrite(blueLed, LOW);
      prevSerialTime2 = millis();
    }
  }
}

void httpsPost()
{
  //task A
  if (taskA.previousPost == 0 || (millis() - taskA.previousPost > taskA.ratePost))
  {
    taskA.previousPost = millis();

    //do task
    //Serial.print("Free Heap: ");
    //Serial.println(ESP.getFreeHeap());

    fetch.begin(API);
    fetch.addHeader("Content-Type", "application/json");
    fetch.POST(JSONmessageBuffer);

    while (fetch.busy())
    {
      //serialData();
      if (fetch.available())
      {
        Serial.write(fetch.read());
      }
      else{
        Serial.println("(Error) -> The HTTPS response stopped working!!!");
      }
    }
    fetch.clean();
  }
}

/*void httpsGet()
{
  if (taskB.previousGet == 0 || millis() - taskB.previousGet > taskB.rateGet)
  {
    taskB.previousGet = millis();

    fetch.GET("https://lylasolutions.000webhostapp.com/db.json");

    //Serial.print(fetch.readString());
    String json = fetch.readString();
    const size_t capacity = JSON_OBJECT_SIZE(4) + 70;
    DynamicJsonDocument doc(capacity);
    DeserializationError error = deserializeJson(doc, json);
    if (error)
    {
      Serial.print(F("deserializeJson() failed: "));
      Serial.println(error.c_str());
    }

    long meter_id = doc["meter_id"];        
    const char *customer_name = doc["customer_name"];
    float power_usage = doc["power_usage"];      
    float power_balance = doc["power_balance"];     

    Serial.print("meter_id: ");
    Serial.println(meter_id);

    Serial.print("customer_name: ");
    Serial.println(customer_name);

    Serial.print("power_usage: ");
    Serial.println(power_usage);

    Serial.print("power_balance: ");
    Serial.println(power_balance);

    Serial.println("");
    fetch.clean();
  }
}*/

void loop()
{
  // put your main code here, to run repeatedly:
  //software interrupts
  WiFiManager.loop();
  updater.loop();
  httpsPost();

  /*** ArduinoJSON v6 was used to collect JsonData from software serial*/
  if (linkSerial.available())
  {
    const size_t capacity = JSON_OBJECT_SIZE(23) + 310;
    DynamicJsonDocument doc(capacity);
    deserializeJson(doc, linkSerial);
    /*DeserializationError error = deserializeJson(doc, linkSerial);
    if (error)
    {
      Serial.print(F("deserializeJson() failed: "));
      Serial.println(error.c_str());
    }*/

    serializeJson(doc, JSONmessageBuffer);
    //Serial.println(JSONmessageBuffer);

    //snprintf(jsonData, sizeof(jsonData), JSONmessageBuffer);
    //Serial.print("Publish message: ");
    //Serial.println(jsonData);
  }

  //httpsGet();
}