Timer error 1 in STM8S003F3P I am writing code to create overflow 1s = Timer 1 to reduce the remaining_sec variable from 60 to 1. But the Timer often hangs for a while at random times. For example, when counting from 60 seconds to 34, it stops there and then continues running after a while. I don't know why? If anyone knows, please help me! Thank you

///////////////////////////////////////
// snippet code file main.c
#include "stm8s.h"

extern volatile uint16_t remain_sec;

void main(){
    _asm("sim\n");
    Clock_config();
    TIM1_config();
    ITC_SetSoftwarePriority(ITC_IRQ_TIM1_OVF, ITC_PRIORITYLEVEL_2);
    _asm("rim\n");

    while (1){
        //notthing to do here
    } 
}

void Clock_config(){
    CLK_DeInit();
    CLK_HSICmd(ENABLE);
    while (CLK_GetFlagStatus(CLK_FLAG_HSIRDY) == RESET);
    CLK_HSIPrescalerConfig(CLK_PRESCALER_HSIDIV1);
}

void TIM1_config(){
    TIM1_DeInit();

    //FCLK/15999 = 1000Hz
    TIM1->PSCRH = 0x3E;
    TIM1->PSCRL = 0x7F;

    //ARR = 999 = 1s overflow
    TIM1->ARRH = 0x03;
    TIM1->ARRL = 0xE7;

    TIM1->IER |= 0x01;  //enable update interrupt
}
///////////////////////////////////////


///////////////////////////////////////
// snippet code file stm8s_it.c

extern volatile uint16_t remain_sec = 0;

INTERRUPT_HANDLER(TIM1_UPD_OVF_TRG_BRK_IRQHandler, 11){
  TIM1->SR1 &= (uint8_t)(~0x01);  //clear UIF

  if(remain_sec > 1){
    --remain_sec;
  }
  //DEBUG
  Serial_print_string("sec=");
  Serial_print_int(remain_sec);
  Serial_print_string("\n");
}
///////////////////////////////////////

I tried running for 5 seconds then it works properly