Почему нужно дважды нажать кнопку чтобы вызвать действие?

По нажатию кнопок true/false нужно вывести надпись correct/incorrect и перелистнуть на следующий вопрос одновременно а по нажатию на back перелистнуть на предыдущий вопрос. До использования ViewModel все было нормально но теперь нужно дважды нажать на кнопку чтобы случилось действие. Как быть? В чем моя ошибка? MainActivity.kt

class MainActivity : AppCompatActivity() {
private lateinit var trueButton: Button
private lateinit var falseButton: Button
private lateinit var backButton: Button
/*nextButton*/
private lateinit var questionTextView: TextView

private var k = 0
private fun checkAnswer(userAnswer: Boolean) {

    val correctAnswer = quizViewModel.currentQuestionAnswer


    val messageResId = if (userAnswer == correctAnswer) {

        k+=1
        R.string.correct_toast


    } else {
        R.string.incorrect_toast
    }

    Toast.makeText(
        this, messageResId,
        Toast.LENGTH_SHORT
    ).apply { setGravity(Gravity.TOP, 0, 0) }.show()
}
private fun result(){

    if(quizViewModel.currentIndex==quizViewModel.f) {

        var str = "Your result is $k out of ${quizViewModel.c}"
        Toast.makeText(
            this, str,
            Toast.LENGTH_SHORT
        ).show()

    }


}
private val quizViewModel: QuizViewModel by lazy{
    val factory = QuizViewModelFactory()
    ViewModelProvider(this, factory).get(QuizViewModel::class.java)
}
@SuppressLint("MissingInflatedId")
override fun onSaveInstanceState(savedInstanceState: Bundle) {
    super.onSaveInstanceState(savedInstanceState)
    Log.i(TAG,
        "onSaveInstanceState")
    savedInstanceState.putInt(KEY_INDEX,
        quizViewModel.currentIndex)
}

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    Log.d(TAG, "onCreate(Bundle?) called")
    setContentView(R.layout.activity_main)
    Log.d(TAG, "Got a QuizViewModel:$quizViewModel")
    val currentIndex = savedInstanceState?.getInt(KEY_INDEX, 0) ?: 0
    quizViewModel.currentIndex = currentIndex
    trueButton = findViewById(true_button)
    falseButton = findViewById(false_button)
    backButton = findViewById(back_button)
    /*nextbutton*/
    fun updateQuestion() {
        val questionTextResId = quizViewModel.currentQuestionText
        questionTextView.setText(questionTextResId)
    }
    fun backQuestion(){
        val questionTextResIdBack = quizViewModel.currentQuestionText
        questionTextView.setText(questionTextResIdBack)
    }


    questionTextView = findViewById(question_text)
    trueButton.setOnClickListener { view: View ->
        checkAnswer(true)
        updateQuestion()
        quizViewModel.moveToNext()


        result()

    }
    falseButton.setOnClickListener { view: View ->
        checkAnswer(false)
        updateQuestion()
        quizViewModel.moveToNext()


        result()

    }
    backButton.setOnClickListener { view: View ->


        if(quizViewModel.currentIndex>=0){
            quizViewModel.moveToPrevious()
            backQuestion()

        }
    }

    val questionTextResId = quizViewModel.currentQuestionText

    questionTextView.setText(questionTextResId)

}
...

QuizViewModel

private const val TAG = "QuizViewModel"
class QuizViewModel: ViewModel() {
    var currentIndex = 0
    private val questionBank = listOf(
        Question(R.string.question_australia,
            true),
        Question(R.string.question_oceans,
            true),
        Question(R.string.question_mideast,
            false),
        Question(R.string.question_africa,
            false),
        Question(R.string.question_americas,
            true),
        Question(R.string.question_asia, true)
    )
    val currentQuestionAnswer: Boolean
        get() = questionBank[currentIndex].answer
    val currentQuestionText: Int
        get() = questionBank[currentIndex].textResId
    fun moveToNext() {
        currentIndex = (currentIndex + 1) % questionBank.size
    }
    fun moveToPrevious() {
        currentIndex = (currentIndex - 1) % questionBank.size
    }
    val f = questionBank.size-1
    val c = questionBank.size

}