zoom bug Completed

import 'dart:async';

import 'package:flutter/material.dart';
import 'package:syncfusion_flutter_charts/charts.dart';
import 'package:intl/intl.dart';

void main() {
  runApp(MaterialApp(
    home: TestPage(),
  ));
}

class TestPage extends StatefulWidget {
  @override
  _TestPageState createState() => _TestPageState();
}

class _TestPageState extends State<TestPage> {
  Future future;

  @override
  void initState() {
    super.initState();
    future = Future.delayed(Duration(seconds: 1));
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),
      body: SfCartesianChart(
        series: [
          LineSeries<Datum, DateTime>(
            dataSource: [
              Datum(DateTime(2020, 7, 1), 3),
              Datum(DateTime(2020, 7, 2), 1),
              Datum(DateTime(2020, 7, 3), 4),
              Datum(DateTime(2020, 7, 4), 8),
              Datum(DateTime(2020, 7, 5), 5),
              Datum(DateTime(2020, 7, 6), 1),
              Datum(DateTime(2020, 7, 7), 3),
              Datum(DateTime(2020, 7, 8), 7),
              Datum(DateTime(2020, 7, 9), 2),
            ],
            xValueMapper: (Datum datum, _) => datum.x,
            yValueMapper: (Datum datum, _) => datum.y,
            markerSettings: MarkerSettings(
              isVisible: true,
            ),
          ),
        ],
        primaryXAxis: DateTimeAxis(
          dateFormat: DateFormat.Md().add_Hm(),
          zoomPosition: 1,
          zoomFactor: 0.2,
        ),
        primaryYAxis: NumericAxis(
          anchorRangeToVisiblePoints: false,
        ),
        zoomPanBehavior: ZoomPanBehavior(
          enablePanning: true,
          enablePinching: true,
          zoomMode: ZoomMode.x,
        ),
        onZooming: (arg) => print('ZoomFactor: ${arg.previousZoomFactor} --> ${arg.currentZoomFactor}, ZoomPosition: ${arg.previousZoomPosition} --> ${arg.currentZoomPosition}'),
      ),
    );
  }
}

class Datum {
  DateTime x;
  num y;

  Datum(this.x, this.y);
}

When user try to zoom out the chart until zoomFactor = 1, the zoomFactor suddenly reset to initial value i.e. 0.2.