Flutter iOS rendering glitches

main.dart

import 'package:flutter/material.dart';
import 'package:flutter_google_ad_manager/flutter_google_ad_manager.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  MyHomePage({Key key}) : super(key: key);

  final _dummyItems = [
    "a",
    "b",
    "c",
    "d",
    "e",
    "f",
    "g",
    "h",
    "i",
    "j",
    "l",
    "m",
    "n"
  ];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        body: CustomScrollView(
      slivers: <Widget>[
        SliverAppBar(
          key: const Key("appbar"),
          expandedHeight: 185,
          // MediaQuery.of(context).size.height * 0.2,
          forceElevated: false,
          flexibleSpace: Text("Header"),
          title: Text("Title"),
        ),
        SliverToBoxAdapter(
          key: Key("ad_top_banner"),
          child: DFPBanner(
            adUnitId: "",
            isDevelop: true,
            adSize: DFPAdSize.BANNER,
          ),
        ),
        SliverList(
            key: const Key("list"),
            delegate: SliverChildBuilderDelegate(
                (ctx, index) => Text(
                      _dummyItems[index],
                      style: TextStyle(fontSize: 28, height: 2),
                    ),
                childCount: _dummyItems.length)),
        SliverToBoxAdapter(
          key: const Key("ad_bottom_banner"),
          child: DFPBanner(
            adUnitId: "",
            isDevelop: true,
            adSize: DFPAdSize.BANNER,
          ),
        ),
      ],
    ));
  }
}

pubspec.yaml

name: flutter_app
description: A new Flutter application.

# The following defines the version and build number for your application.
# A version number is three numbers separated by dots, like 1.2.43
# followed by an optional build number separated by a +.
# Both the version and the builder number may be overridden in flutter
# build by specifying --build-name and --build-number, respectively.
# In Android, build-name is used as versionName while build-number used as versionCode.
# Read more about Android versioning at https://developer.android.com/studio/publish/versioning
# In iOS, build-name is used as CFBundleShortVersionString while build-number used as CFBundleVersion.
# Read more about iOS versioning at
# https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/CoreFoundationKeys.html
version: 1.0.0+1

environment:
  sdk: ">=2.1.0 <3.0.0"

dependencies:
  flutter:
    sdk: flutter
  flutter_google_ad_manager: ^0.8.0

  # The following adds the Cupertino Icons font to your application.
  # Use with the CupertinoIcons class for iOS style icons.
  cupertino_icons: ^0.1.2

dev_dependencies:
  flutter_test:
    sdk: flutter


# For information on the generic Dart part of this file, see the
# following page: https://www.dartlang.org/tools/pub/pubspec

# The following section is specific to Flutter.
flutter:

  # The following line ensures that the Material Icons font is
  # included with your application, so that you can use the icons in
  # the material Icons class.
  uses-material-design: true

  # To add assets to your application, add an assets section, like this:
  # assets:
  #  - images/a_dot_burr.jpeg
  #  - images/a_dot_ham.jpeg

  # An image asset can refer to one or more resolution-specific "variants", see
  # https://flutter.dev/assets-and-images/#resolution-aware.

  # For details regarding adding assets from package dependencies, see
  # https://flutter.dev/assets-and-images/#from-packages

  # To add custom fonts to your application, add a fonts section here,
  # in this "flutter" section. Each entry in this list should have a
  # "family" key with the font family name, and a "fonts" key with a
  # list giving the asset and other descriptors for the font. For
  # example:
  # fonts:
  #   - family: Schyler
  #     fonts:
  #       - asset: fonts/Schyler-Regular.ttf
  #       - asset: fonts/Schyler-Italic.ttf
  #         style: italic
  #   - family: Trajan Pro
  #     fonts:
  #       - asset: fonts/TrajanPro.ttf
  #       - asset: fonts/TrajanPro_Bold.ttf
  #         weight: 700
  #
  # For details regarding fonts from package dependencies,
  # see https://flutter.dev/custom-fonts/#from-packages