Why is the upload file not saved?

Question

Yii

When I create a new record, it is not saved if I still upload the file. As a result, there is no record id to which to redirect, if you exclude working with files, then the record is created and sent to the view view.
This is what the model looks like:

class Journal extends \yii\db\ActiveRecord
{

    const SCENARIO_CREATE = 'create';
    const SCENARIO_UPDATE = 'update';

    public function scenarios()
    {
        $scenarios = parent::scenarios();
        $scenarios[self::SCENARIO_CREATE] = ['title', 'preview'];
        $scenarios[self::SCENARIO_UPDATE] = ['title'];
        return $scenarios;
    }

    /**
     * @inheritdoc
     */
    public static function tableName()
    {
        return 'journal';
    }

    /**
     * @inheritdoc
     */
    public function rules()
    {
        return [
            [['title', 'preview'], 'required', 'on' => self::SCENARIO_CREATE],
            [['title'], 'required', 'on' => self::SCENARIO_UPDATE],
            [['content'], 'string'],
            [['created_at', 'updated_at'], 'safe'],
            [['title', 'preview'], 'string', 'max' => 150],
            [['description'], 'string', 'max' => 250],
            [['url'], 'string', 'max' => 70],
            [['preview'], 'file', 'extensions' => 'png, jpg, jpeg, gif', 'skipOnEmpty' => true]
        ];
    }
....

Controller method for creating a new entry:

public function actionCreate()
    {
        $this->view->title = 'Создание статьи';
        $this->view->params['breadcrumbs'][] = ['label' => 'Журнал', 'url' => ['panel/journal']];
        $this->view->params['breadcrumbs'][] = $this->view->title;

        $model = new Journal(['scenario' => Journal::SCENARIO_CREATE]);

        if ($model->load(Yii::$app->request->post())) {
            $model->content = Html::decode($model->content);
            $model->url = Translit::t($model->title);
            $model->preview = UploadedFile::getInstance($model, 'preview');

            $path = Yii::$app->params['uploads_path'].'/journal/preview/';
            $model->preview->saveAs($path.$model->preview->name);

            $model->save();

            return $this->redirect(['view', 'id' => $model->id]);
        } else {
            return $this->render('create', [
                'model' => $model,
            ]);
        }
    }

Answer 1

if ($model->load(...)) {
    ...
    if ($model->save()) {
        return $this->redirect(['view', 'id' => $model->id]);
    } 
}

return $this->render('create', [
    'model' => $model,
]);

Answer 2

Do a VarDumper::dump($model->getErrors(), 10, true) after trying to save, see the errors