why the score doesn't appear or even increase , Adobe Animate, HTML5, Javascript

when the value is false, the score will be increased by 10, and i'm add an alert message 

and the text score is update , but when I answered the other questions, It's like the function not executed. It's like the the function executed for the first question

function onClickAnswer(e)
{	
if(IsAnswer==false)
	{
		var item=e.currentTarget;
		if(item.name=="jawaban_benar"+currentPertanyaan.pilihan_jawaban)  
		{
			score+=10;
			console.log("Correct "+score);
			alert("Benar");
			this.text_skor.text=score;
		}else{
			score+=10;
			console.log("Incorrect "+score);
			alert("Salah");
			this.text_skor.text=score;
		}
		IsAnswer=true;
	}
	NextQuestion.bind(this)();
}

In this experiment, I tried only randomizing the questions and not the answers.
Here the all code :

//variabel global
//create array pertanyaan

var data = [{
	pertanyaan_text: "Berapakah Jenis Bekam",
	jawaban_benar: "2",
	pilihan_jawaban: ["1", "3", "2","4"]
}, {
	pertanyaan_text: "Bekam yang dilakukan dengan memberikan perlukaan disebut",
	jawaban_benar: "1",
	pilihan_jawaban: ["Bekam Kering", "Bekam Basah", "Bekam Luncur","Bekam Pijat"]
}, {
	pertanyaan_text: "Salah satu Kontraindikasi Absolut Bekam adalah",
	jawaban_benar: "0",
	pilihan_jawaban: ["Hemofilia", "Hipertensi", "Anak-anak","Sakit Kepala"]
}, ];

var indexPertanyaan = 0;
var currentPertanyaan;
var score = 0;
var IsAnswer=false;

//Fungsi-Fungsi 

function mixed(Items)
{
	var newArray=[];
	var original= Items.concat();
	while(original.length>0)
	{
	  var r =Math.floor(Math.random()*(original.length));
		newArray.push(original[r]);
		original.splice(r,1);
	}
	return newArray;
}

loadPertanyaan.bind(this)();

function loadPertanyaan(){
//Acak Soal
data= mixed(data);
	
//Ambil soal pertama yang baru
currentPertanyaan = data[indexPertanyaan];
	
//Tampilkan pertanyaan
this.mc_kuis.txt_Pertanyaan.text = currentPertanyaan.pertanyaan_text;
	
//Acak pilihan jawaban dan menampilkan pada button
//var acakJawaban = mixed(currentPertanyaan.pilihan_jawaban);
this.mc_kuis.bt_jawaban1.txt_Jawaban.text = currentPertanyaan.pilihan_jawaban[0];
this.mc_kuis.bt_jawaban2.txt_Jawaban.text = currentPertanyaan.pilihan_jawaban[1];
this.mc_kuis.bt_jawaban3.txt_Jawaban.text = currentPertanyaan.pilihan_jawaban[2];
this.mc_kuis.bt_jawaban4.txt_Jawaban.text = currentPertanyaan.pilihan_jawaban[3];
}

this.mc_kuis.bt_jawaban1.on("click",onClickAnswer.bind(this));
this.mc_kuis.bt_jawaban2.on("click",onClickAnswer.bind(this));
this.mc_kuis.bt_jawaban3.on("click",onClickAnswer.bind(this));
this.mc_kuis.bt_jawaban4.on("click",onClickAnswer.bind(this));

console.log(loadPertanyaan);
console.log(onClickAnswer);

function onClickAnswer(e)
{	
if(IsAnswer==false)
	{
		var item=e.currentTarget;
		if(item.name=="jawaban_benar"+currentPertanyaan.pilihan_jawaban)  
		{
			score+=10;
			console.log("Correct "+score);
			alert("Benar");
			this.text_skor.text=score;
		}else{
			score+=10;
			console.log("Incorrect "+score);
			alert("Salah");
			this.text_skor.text=score;
		}
		IsAnswer=true;
	}
	NextQuestion.bind(this)();
}

function NextQuestion()
{
	indexPertanyaan++;
	if(indexPertanyaan == data.length)
	{
		alert("Selesai")
	}else{
		currentPertanyaan=data[indexPertanyaan];
		loadPertanyaan.bind(this)();
	}
}