iOS: AVSpeechSynthesizer doesn't work after changing language

XCode 8.2.1, Swift 3, iOS 10.0, iPhone 6s

I use this code for AVSpeechSynthesizer

private func listenText(text: String, language: String) {

      let speechLanguage: String = STTLanguagesManager.shared.getAppleLanguageWithCode(code: language);      stopListening();

      let audioSession = AVAudioSession.sharedInstance()

      do {

           try audioSession.setCategory(AVAudioSessionCategoryPlayback)

           try audioSession.setMode(AVAudioSessionModeDefault)

           try audioSession.setActive(true, with: .notifyOthersOnDeactivation)

      } catch {

           print("audioSession properties weren't set because of an error.") return;

      }

      let synthUtterance = AVSpeechUtterance(string: text);

      synthUtterance.rate = currentSpeechRate;

     synthUtterance.voice = AVSpeechSynthesisVoice(language: speechLanguage);

      synthesizeEngine = AVSpeechSynthesizer();

     synthesizeEngine!.speak(synthUtterance);

}

private func stopListening() {

     if (self.synthesizeEngine != nil && self.synthesizeEngine!.isSpeaking) {

          self.synthesizeEngine!.stopSpeaking(at: .immediate);

      }

      self.synthesizeEngine = nil;

}

Sometimes when I change language synthesizer doesn't speak anything. I noticed it is true for Chinese and Arabic languages.

I implemented AVSpeechSynthesizerDelegate and when I have this problem synthesizer fired didStart and didFinish delegates, without willSpeakRangeOfSpeechString.

How can I fix it?