Saving CMSampleBufferRef causes random crashes

Question

I use captureOutput:didOutputSampleBuffer:fromConnection:to track frames. For my use case, I only need to save the last frame and use it if the application goes into the background.

This is a sample from my code:

@property (nonatomic, strong) AVCaptureVideoDataOutput *videoDataOutput;
@property (atomic) CMSampleBufferRef currentBuffer;

- (UIImage *) imageFromSampleBuffer:(CMSampleBufferRef) sampleBuffer
{
    // Get a CMSampleBuffer Core Video image buffer for the media data
    CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
    // Lock the base address of the pixel buffer
    CVPixelBufferLockBaseAddress(imageBuffer, 0);

    // Get the number of bytes per row for the pixel buffer
    void *baseAddress = CVPixelBufferGetBaseAddress(imageBuffer);

    // Get the number of bytes per row for the pixel buffer
    size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);
    // Get the pixel buffer width and height
    size_t width = CVPixelBufferGetWidth(imageBuffer);
    size_t height = CVPixelBufferGetHeight(imageBuffer);

    // Create a device-dependent RGB color space
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

    // Create a bitmap graphics context with the sample buffer data
    CGContextRef con = CGBitmapContextCreate(baseAddress, width, height, 8,
                                             bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
    // Create a Quartz image from the pixel data in the bitmap graphics context
    CGImageRef quartzImage = CGBitmapContextCreateImage(con);
    // Unlock the pixel buffer
    CVPixelBufferUnlockBaseAddress(imageBuffer,0);

    // Free up the context and color space
    CGContextRelease(con);
    CGColorSpaceRelease(colorSpace);

    // Create an image object from the Quartz image
    //    UIImage *image = [UIImage imageWithCGImage:quartzImage];
    UIImage *image =  [UIImage imageWithCGImage:quartzImage scale:[[UIScreen mainScreen] scale] orientation:UIImageOrientationRight];

    // Release the Quartz image
    CGImageRelease(quartzImage);

    return (image);
}
//[self.videoDataOutput setSampleBufferDelegate:self queue:self.sessionQueue];

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{
    CFRetain(sampleBuffer);

    @synchronized (self) {
        if (_currentBuffer) {
            CFRelease(_currentBuffer);
        }
        self.currentBuffer = sampleBuffer;
    }
}

- (void) goingToBackground:(NSNotification *) notification
{
    UIImage *snapshot = [self imageFromSampleBuffer:_currentBuffer];

    //Doing something with snapshot...
}

The problem is that in some cases I get this failure from the inside imageFromSampleBuffer:

<Error>: copy_read_only: vm_copy failed: status 1.

Accident occurs on CGImageRef quartzImage = CGBitmapContextCreateImage(con);

What am I doing wrong?