javascript countdowntimer random ajax call executing multiple times

There are 30 boxes on the page and every box carries itemtime displaying random time in m:ss formate . Every second countdown() decrements the time to -1 seconds. when any itemtime reaches 0:00 time,new content is fetched by ajax call inside function loadbox().

PROBLEM:

Sometimes the ajax call is multiple times,thus updating the box in quick succession. I have logged calls in the getnewboxcontent.php, it is really multiple times with same data paraments. Tried many solutions already given on SOF.But still not solved. Not sure what I am missing... I tried like :

1.

 loadBox(boxnum,function(output)
{
   var boxName = 'boxplace'+boxnum;
   $('#'+boxName).html(data);
});

2. cache=false


3. clearing and setting timer before and after the ajax call

---

Many thanks!!

   `var countDownTimer = setInterval(function(){countDown()},1000);
    function countDown(){
       for(var i=1;i<=<?php echo $numberofboxes;?>;i++){
          var timeBox = document.getElementById('itemtime'+i);
          if (timeBox != null ) {    
              var lastTime = timeBox.innerHTML;
              var timePart = lastTime.split(":");
              var minutes = parseInt(timePart[0]);
              var seconds = parseInt(timePart[1]);
              if (minutes==0&&seconds==0){
                     loadBox(i); 
                }
                else{
                if (minutes>0&&seconds==0){minutes--;seconds=59}
                else{seconds--;}
                if (seconds < 10){seconds = "0"+seconds;}
                timeBox.innerHTML = minutes+":"+seconds;
                }
           }
       }
    }
    function loadBox(boxNumber){
        var eTString = '#extratime'+boxNumber;
        var extraTime = $(eTString).val();
        var boxName = 'boxplace'+boxNumber;
        var itemIDk=$('#item'+boxNumber).val();
        $.get("functions/getnewboxcontent.php?boxNumber="+boxNumber+"&extraTime="+extraTime+"&reload=true"+"&itemnum="+itemIDk, function(data) {
            var boxName = 'boxplace'+boxNumber;
            document.getElementById(boxName).innerHTML = data;
            console.log(boxNumber+' - '+itemIDk);   
        });
    }
    `