谷歌api一段时间工作正常，有时不

Some times this code works properly but some times it not update the location and icon . first it load the map with all the user location and it's marker icon according to the status of user , then i use the time interval function to update the location and status of the user .but it didn't update the location and marker icon on map .it get proper response from ajax .
Please help me , already check the api credential and enabled api

 var locations =["user","latitude","longitude","1",$order_id,$req_address,$dr_address,"2"];
var map = new google.maps.Map(document.getElementById('map'), {
  zoom: 8,
  center: new google.maps.LatLng(current_lat, current_lon),
  mapTypeId: google.maps.MapTypeId.ROADMAP
});

var infowindow = new google.maps.InfoWindow({

});

var marker, i,name;

for (i = 0; i < locations.length; i++) {

     if(locations[i][3]==1)
     {
        //driver available
        dr_icon=Settings.base_url+'assets/map_icons/driver_available.png';
     }
     if(locations[i][3]==2)
     {
        //driver boocked
        dr_icon=Settings.base_url+'assets/map_icons/driver_boocked.png';
     }
     if(locations[i][3]==4)
     {
        //driver refilling
        dr_icon=Settings.base_url+'assets/map_icons/driver_refilling.png';
     }
     if(locations[i][3]==5)
     {
        //driver offline
        dr_icon=Settings.base_url+'assets/map_icons/driver_offline.png';
     }
  marker = new google.maps.Marker({
    icon:dr_icon,
    position: new google.maps.LatLng(locations[i][1], locations[i][2]),
    map: map
  });

  google.maps.event.addListener(marker, 'click', (function(marker, i) {
    return function() {
        var order_id = locations[i][4];
        var req_address = locations[i][5];
        var name= locations[i][0];
        var dr_address=locations[i][6];
        var iwin='<div class="col">'+
        '<div class="card gradient-45deg-light-blue-cyan gradient-shadow">'+
        '<div class="card-content white-text"><span class="card-title">'+name+'</span>'+
          '<p>Order id : '+order_id+'<p></p> Address : '+req_address+
              '<p></p>Driver : '+dr_address+'</p>'+
        '</div><div class="card-action">'+
        '<a href="'+Settings.base_url+'index.php/Adminmap/trackCustomerDriver/'+locations[i][7]+'" class="waves-effect waves-light btn gradient-45deg-red-pink">Tracking</a>'+
        '</div> </div> </div>';

     infowindow.setContent(iwin);
     infowindow.open(map, marker);
    }
  })(marker, i));
}
/*change driver position*/   setInterval(function(){ 
    var myKeyVals = {country_id : $("#country").val(),state_id : $("#state").val(),city_id : $("#city").val(),service_area_id : $("#service_area").val(),driver_name : $("#driver_name").val()};

$.ajax({
        url: Settings.base_url+"index.php/Adminmap/driverLocationTracking",
        type: "POST",
        data: myKeyVals,
        success: function(result1){
        //console.log(result1);
            obj=JSON.parse(result1);
            console.log(obj);

            for (i = 0; i < obj.length; i++) { 
             /* marker = new google.maps.Marker({
                icon:'http://cdn.leafletjs.com/leaflet-0.6.4/images/marker-icon.png',
                position: new google.maps.LatLng(obj[i][1], obj[i][2]),
                map: map
              });

              google.maps.event.addListener(marker, 'click', (function(marker, i) {
                return function() {
                  infowindow.setContent(obj[i][0]);
                  infowindow.open(map, marker);
                }
              })(marker, i));*/
              if(obj[i][3]==1)
             {
                //driver available
                dr_icon=Settings.base_url+'assets/map_icons/driver_available.png';
             }
             if(obj[i][3]==2)
             {
                //driver boocked
                dr_icon=Settings.base_url+'assets/map_icons/driver_boocked.png';
             }
             if(obj[i][3]==4)
             {
                //driver boocked
                dr_icon=Settings.base_url+'assets/map_icons/driver_refilling.png';
             }
             if(obj[i][3]==5)
             {
                //driver offline
                dr_icon=Settings.base_url+'assets/map_icons/driver_offline.png';
             }
              var lat=parseFloat(obj[i][1]);
              var lon=parseFloat(obj[i][2]);

              latlong=new google.maps.LatLng(lat,lon)
              marker.setPosition(latlong);
              marker.setIcon(dr_icon);
            }
        }
    });
}, 2000);