UIImagePickerController didFinishPickingMediaWithInfo sometime is not called - ios

Question

Hi Im making altered reality app. My main controller is derived from UIImagePickerController. Here is how I create it:
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
if (!self.overlayController) {
if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]) {
self.sourceType = UIImagePickerControllerSourceTypeCamera;
self.cameraCaptureMode = UIImagePickerControllerCameraCaptureModePhoto;
self.cameraDevice = UIImagePickerControllerCameraDeviceRear;
self.showsCameraControls = false;
self.allowsEditing = false;
self.overlayController = [[[ControlsViewController alloc] initWithNibName:#"ControlsViewController" bundle:[NSBundle mainBundle] picker:self] autorelease];
[self.view addSubview:self.overlayController.view]; // need to add as subview otherwise mouse events captured by UIImagePickerController
self.overlayController.view.frame = CGRectMake(0,0, self.view.frame.size.width, self.view.frame.size.height);
}
}
[cameraControls setCamera:self];
}
Basically controller exists through whole lifecycle of the app. Now when I take photo with code below most of the time it works fine but sometime didFinishPickingMediaWithInfo isn't called. Usual behavior is I see camera focus starts adjust blur-in/out and then it stabilizes but didFinishPickingMediaWithInfo will never be called. Looks like if camera goes into some kind of calibration mode it may not fire this event. Anyone have solution? I hope there is maybe some kind of extra callback (like error processing Im missing).
I can even hear camera shutters simulated sound interrupted when camera goes into that weird calibration mode.
//self.cameraPicker points to the instance of my main controller that I created earlier
-(void) setCamera:(UIImagePickerController *)picker {
self.cameraPicker = picker;
picker.delegate = self;
}
-(void) takePicture {
[self.cameraPicker takePicture];
}
-(void) imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info {
NSLog(#"Picture ready");
}