Flutter app working on emulator, but not on android device

I am just developing one simple Flutter application. I use Provider library to manage state in application, but I have some problems.

Application works fine, when I run it on emulator or when I run it through debug mode ("flutter run" command) on my Samsung S9 device.

As soon as I build the .app file and I try to run it on device, it doesn't work as it should. Application doesn't re-render when I change state in my Provider class (it should react and re-render as soon as some property from Provider has changed).

It doesn't make sense to me. Where can be a problem?

Provider class

    class GlobalProvider with ChangeNotifier{
        BuildContext context;
        String _currentLang = 'SL';
        String get currentLanguage => _currentLang;

        set currentLanguage(String lang){
            _currentLang = lang;
            notifyListeners();
        }
    }

When I change the value of _currentLang property, all the widgets, that use that property, should be re-rendered.

As I said, it works good on emulator and on device, but when I build the .app file and install it on Samsung S9 device, it doesn't re-render.

Thanks for your help.