Flutter - Local Notifications fail in release mode - flutter

Question

I added the flutter_local_notifications plugin to schedule notifications. In the debug version everything works well for both emulators and real devices.
However, when I build the app
flutter build apk --split-per-abi
and install the package on a device and run the app, when it comes to the code part that marks the notification (I supposed...) , the app crashes
How do I find out what's wrong?
I followed the plugin developers instructions and changed the manifest file:
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.explika">
<uses-permission android:name="android.permission.INTERNET" />
<!-- Tudo relacionado com as notificações -->
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>
<uses-permission android:name="android.permission.VIBRATE" />
<!-- Fim relacionado com notificações -->
<!-- io.flutter.app.FlutterApplication is an android.app.Application that
calls FlutterMain.startInitialization(this); in its onCreate method.
In most cases you can leave this as-is, but you if you want to provide
additional functionality it is fine to subclass or reimplement
FlutterApplication and put your custom class here. -->
<application
android:name="io.flutter.app.FlutterApplication"
android:label="Explika"
android:icon="#mipmap/ic_launcher">
<receiver android:name="com.dexterous.flutterlocalnotifications.ScheduledNotificationReceiver" />
<activity
android:name=".MainActivity"
android:launchMode="singleTop"
android:theme="#style/LaunchTheme"
android:configChanges="orientation|keyboardHidden|keyboard|screenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
android:hardwareAccelerated="true"
android:windowSoftInputMode="adjustResize">
<!-- This keeps the window background of the activity showing
until Flutter renders its first frame. It can be removed if
there is no splash screen (such as the default splash screen
defined in #style/LaunchTheme). -->
<meta-data
android:name="io.flutter.app.android.SplashScreenUntilFirstFrame"
android:value="true" />
<intent-filter>
<action android:name="android.intent.action.MAIN"/>
<category android:name="android.intent.category.LAUNCHER"/>
</intent-filter>
</activity>
</application>
</manifest>

Answer 1

I found out what is causing the application to crash:
[ERROR: flutter / shell / platform / android / platform_view_android_jni.cc (39)] java.lang.AssertionError: java.lang.NoSuchFieldException: Drawable
However, this only happened in the Release version. The solution consists of customizing the ProGuard configuration file and the build.gradle file following the instructions on the plugin page.
I didn't do these steps because until then the Release version worked without problems and because I thought ProGuard configuration file would only be necessary in case want to publish on the Play Store.