Django - UnicodeDecodeError: 'utf-8' codec can't decode byte 0xff in position 0: invalid start byte

Пытаюсь прогнать view-класс через тест с использованием трех фикстур (для продуктов, заказов и пользователей), получаю следующую ошибку: "UnicodeDecodeError: 'utf-8' codec can't decode byte 0xff in position 0: invalid start byte". Фикстуры ничем сторонним не открывал. Работаю на windows 10 в pycharm. Код самого теста:

class OrdersExportTestCase(TestCase):
    fixtures = [
        'products-fixture.json',
        'orders-fixture.json',
        'users-fixture.json'
    ]

    @classmethod
    def setUpClass(cls):
        super().setUpClass()
        cls.user = User.objects.create_user(username='test', password='test')
        cls.user.is_staff = True
        cls.user.save()

    def setUp(self) -> None:
        self.client.force_login(self.user)

    def test_get_orders_view(self):
        response = self.client.get(reverse(
            'shopapp:orders_export'
        ))
        self.assertEqual(response.status_code, 200)
        orders = Order.objects.order_by('pk').all()
        expected_data = [
            {
                'pk': order.pk,
                'delivery_address': order.delivery_address,
                'promocode': order.promocode,
                'user_id': order.user.pk,
                'products': [product.pk for product in order.products.all()]
            }
            for order in orders
        ]
        orders_data = response.json()
        self.assertEqual(orders_data['orders'], expected_data)

    @classmethod
    def tearDownClass(cls):
        cls.user.delete()

Код view-класса:

@method_decorator(user_passes_test(lambda u: u.is_staff), name='dispatch')
class OrdersExportView(View):
    def get(self, request: HttpRequest) -> JsonResponse:
        orders = Order.objects.order_by('pk').all()
        orders_data = [
            {
                'pk': order.pk,
                'delivery_address': order.delivery_address,
                'promocode': order.promocode,
                'user_id': order.user.pk,
                'products': [product.pk for product in order.products.all()]
            }
            for order in orders
        ]

        return JsonResponse({'orders': orders_data})

Фикстуры создавал следующими командами:

python manage.py dumpdata shopapp.Product > shopapp/fixtures/products-fixture.json
python manage.py dumpdata shopapp.Order > shopapp/fixtures/orders-fixture.json
python manage.py dumpdata auth.User > shopapp/fixtures/users-fixture.json