How to allow keyguard / lock screen to lock phone after unlocking the device with setShowWhenLocked(true);

I am creating a video calling app and have the following code which is called when the application receives a push notification - it unlocks the screen and presents an 'incoming call' user interface:

public class MainActivity extends ReactActivity {

  @Override
  protected String getMainComponentName() {
    return "x";
  }

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O_MR1) {
      setShowWhenLocked(true);
      setTurnScreenOn(true);
    }
    getWindow().addFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN | WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED
        | WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON | WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
        | WindowManager.LayoutParams.FLAG_DISMISS_KEYGUARD);
  }
}

This works fine when a call is incoming - the user can interact with the app using the UI presented. However, the problem is is that if the app is in the foreground and the phone is then locked, when the unlock button is pressed on the side of the phone, the app is displayed, instead of the keyguard / lock screen being displayed. It permanently allows access to the app if it is in the foreground and the phone is locked and the unlock button is pressed.

I want the app to appear when the it receives a push notification and the screen is locked, but I also want the user to be able to lock the device fully and not give the user access to the app after pressing the lock button.

How can I achieve this? Thanks in advance.