Black screen on iPhone 4 iOS 7 video recording?

Question

I have an app that uses the front camera and the microphone to record a video. I have tried it on an iPhone 4S with iOS 6, iPad 2 iPhone 5 and iPhone 5S with iOS 7, and the video is recorded and played correctly.

But on an iPhone 4 with iOS 7.0.4 sometimes there's a black screen with audio, and sometimes there's the video but without any audio.

When this bug appears, any other app on the iPhone will record just a black screen or will record video without audio. I have to restart the iPhone 4 in order to try to record again.

Is this a bug on iOS 7, or is it a problem with my code? Have anyone experienced this as well?

Here's the recording code:

- (void)setupSession {

    AVCaptureSession *session = [[AVCaptureSession alloc] init];

    [session beginConfiguration];

    // Recording in low resolution to boost up video capturing on lower-end devices
    if ([session canSetSessionPreset:AVCaptureSessionPresetMedium]) {
        session.sessionPreset = AVCaptureSessionPresetMedium;
        NSLog(@"%@", session.sessionPreset);
    }

    if (!self.frontCamera || !self.microphone) {
        NSLog(@"Unable to start recording session");
        return;
    }

    // Adding camera capturing input
    NSError *error;
    AVCaptureDeviceInput *cameraInput = [AVCaptureDeviceInput deviceInputWithDevice:self.frontCamera
                                                                              error:&error];
    if (!cameraInput) {
        NSLog(@"Couldn't retrieve camera input: %@", [error localizedDescription]);
        return;
    }

    // Adding audio capturing input
    error = nil;
    AVCaptureDeviceInput *audioInput = [AVCaptureDeviceInput deviceInputWithDevice:self.microphone
                                                                             error:&error];
    if (error) {
        NSLog(@"Couldn't retrive camera input: %@", [error localizedDescription]);
        return;
    }

    if ([session canAddInput:cameraInput] && [session canAddInput:audioInput]) {
        [session addInput:cameraInput];
        [session addInput:audioInput];
    } else {
        NSLog(@"Session input could not be added");
    }

    // Adding movie file output
    AVCaptureMovieFileOutput *movieFileOutput = [[AVCaptureMovieFileOutput alloc] init];

    if ([session canAddOutput:movieFileOutput]) {
        [session addOutput:movieFileOutput];
        self.movieFileOutput = movieFileOutput;
    } else {
        return;
        NSLog(@"Session output could not be added");
    }

    AVCaptureConnection *videoConnection = movieFileOutput.connections[0];
    if ([videoConnection isVideoOrientationSupported]) {
        videoConnection.videoOrientation = AVCaptureVideoOrientationLandscapeLeft;
    }

    // Listen for notifications
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(receivedCaptureSessionNotification:)
                                                 name:nil
                                               object:session];

    _session = session;

    [session commitConfiguration];

    self.canRecord = YES;
}`

And this is my dealloc:

- (void)dealloc {
    [[NSNotificationCenter defaultCenter] removeObserver:self
                                                    name:AVPlayerItemDidPlayToEndTimeNotification
                                                  object:self.session];

    if ([self.session isRunning]) {
        for(AVCaptureInput *input1 in self.session.inputs) {
            [self.session removeInput:input1];
        }

        for(AVCaptureOutput *output1 in self.session.outputs) {
            [self.session removeOutput:output1];
        }

    [self.session stopRunning];
    }
    self.session=nil;

    NSLog(@"gamerecording dealloc'd");

}

I was logging my session inputs on dealloc, and the mic and front camera are always listed.

If more information is needed, I can include it.