AVAudioSession iOS 12.4.1 Impossible to record audio with Timer.scheduledTimer when the app is in background

Question

Timer works fine even in the background (I can read the logs) but method AVAudioRecorder.record() doesn't ... here the scheduled method:

@objc func timer(){
        os_log("timer")
        if self.audioRecorder == nil {
            //...some stuff
            self.audioRecorder = try AVAudioRecorder(url: audioFileName, settings: settings)
            self.audioRecorder.delegate = self
            self.audioRecorder.record()
        }
    }

the timer settings:

_ = Timer.scheduledTimer(timeInterval: 10.0, target: self, selector: #selector(timer), userInfo: nil, repeats: false)

I have found this issue after iOS 12.4 update.

• I use two different instance of AVAudioSession

• It works perfectly when the app is in foreground

• I play the audio file tapping it and I schedule with timer when to start recorder

• So i start music, I move the app in background, the music still play, the timer fires ... BUT the recorder doesn't want to start ..

Maybe a BUG ?