django file transfer?

Question

JavaScript

I need to upload a file from Django to a web page. The file is being transferred. But it does not open in Excel, and it is visually visible that the file encoding is different.
The greatly simplified code looks like this (we do not pay attention to the serializer and pk transmission - this does not affect the logic):
Server side:

class CEIViewset(GenericViewSet):
    queryset = CompetitionCEI.objects.all()
    permission_classes = (permissions.IsAuthenticated,)
    serializer_class = CompetitionCEISerializer

    @action(detail=False, methods=['POST'], permission_classes=(permissions.IsAuthenticated, ))
    def export_to_xls(self, request):
        ser = self.serializer_class(data=request.data)
        if ser.is_valid():
            pk = ser.validated_data.get('pk')

            with open(os.path.join(settings.BASE_DIR, 'data', 'sample.xls'), 'rb') as f:
                data = f.read()

            response = HttpResponse(data, content_type='application/xls; charset=utf-8')
            response['Content-Disposition'] = 'attachment; filename="sample.xls"'
            return response

Client side:

function exportXLS(pk) {
            $.ajax({
              method: 'POST',
              url: '/api/v1/cei/export_to_xls/',
              csrfmiddlewaretoken: '{{ csrf_token }}',
              contentType: 'application/json',
              responseType: 'blob',
              data: JSON.stringify({
                  pk: {{ object.pk }},
              }),
              success: function (response) {
              }
          }).done(function(response){
                  var newBlob = new Blob([response], {type: "application/xls"});
                  const data = window.URL.createObjectURL(newBlob);
                  var link = document.createElement('a');
                  link.href = data;
                  link.download="sample.xls";
                  link.click();
          })
  }

Original file

Downloadable file

It can be seen that the data is beating. Until I understand - on the client or server side? And how to fix it?