upload obrázkov hlási session error

Zdravím,

mám formulár, ktorý odosiela až 44+ obrázkov a po jeho odoslaní nette hlási túto podivnú chybu:

http://prntscr.com/3asfi0

Ak vypnem developer mode, tak nahrá prvých 20 obrázkov a skončí to bez problémov. V error logu však vyskakujú tieto dve chyby:

[2014-04-17 09-55-02] PHP User Notice: Possible problem: you are starting session while already having some data in output buffer. This may not work if the outputted data grows. Try starting the session earlier. in /var/www/vhosts/lvps178-77-74-72.dedicated.hosteurope.de/psdcoding.sk/sub/iloveny/vendor/nette/nette/Nette/Http/Session.php:543  @  http://iloveny.psdcoding.sk/slider/edit/14?do=sliderForm-submit
[2014-04-17 09-55-02] PHP User Notice: Possible problem: you are sending a HTTP header while already having some data in output buffer. Try OutputDebugger or start session earlier. in /var/www/vhosts/lvps178-77-74-72.dedicated.hosteurope.de/psdcoding.sk/sub/iloveny/vendor/nette/nette/Nette/Http/Response.php:315  @  http://iloveny.psdcoding.sk/slider/edit/14?do=sliderForm-submit

dumpy som z kódu celkom odstránil, čiže to by nemal byť problém. Prosím niekto nejaké nápady??

kód formulára je nasledovný:

public function createComponentSliderForm(){
	$form = new Form;

	$form->addText('name', 'Name:')
		->setAttribute('placeholder', 'Slides set #ID (default)');
	$form->addText('activeFrom', 'Active from:')
		->setAttribute('placeholder', 'NOW (default)');

	$form->addDynamic('slides', function (Nette\Forms\Container $slides){
		$slides->addText('headline', 'Headline:')
			->addRule(Form::REQUIRED, 'Please fill in headline.');
		$slides->addTextArea('text', 'Text:')
			->addRule(Form::REQUIRED, 'Please fill in text.');
		$slides->addText('link', 'Target:')
			->getControlPrototype()
			->class('autocomplete');
		$slides->addHidden('link_type')
			->getControlPrototype()
			->class('link_type');
		$slides->addHidden('link_id')
			->getControlPrototype()
			->class('link_id');

		$slides->addUpload('android', 'Android:');
		$slides->addUpload('iphone4', 'iPhone4:');
		$slides->addUpload('iphone5', 'iPhone5:');
		$slides->addUpload('ipad', 'iPad:');

		$slides->addCheckBox('active', 'Active')
			->getControlPrototype()
			->class('active');;

		$keys = array('android', 'iphone4', 'iphone5', 'ipad');
		foreach($keys as $i){
			foreach($keys as $k){
				if($i!=$k)
					$slides[$i]
						->addConditionOn($slides[$k], Form::FILLED)
						->addRule(Form::REQUIRED, 'Please submit every type of the slide image.');
			}
		}
	});

	$form->setDefaults($this->data);

	$form->addSubmit('submit', 'Save');
	$form->onValidate[] = $this->sliderValidate;
	$form->onSuccess[] = $this->sliderSucceeded;
	return $form;
}

public function sliderValidate($form){
	if(!empty($form->values->activeFrom) && strtotime($form->values->activeFrom) < 1)
		$form->addError('Invalid date for active from field.');
	if(count($form->values->slides) < \App\Model\Slider::MIN_SLIDES)
		$form->addError('You need to have at least '.\App\Model\Slider::MIN_SLIDES.' slides.');
}

public function sliderSucceeded($form){
	if(empty($this->data->id)){
		if($id = $this->sliderM->add($form->values)){
			$this->flashMessage('Slider set has been successfully saved.', 'success');
			$this->redirect('Slider:slides');
		}
	}else{
		if($id = $this->sliderM->edit($this->data->id, $form->values)){
			$this->flashMessage('Slider set has been successfully updated.', 'success');
			$this->redirect('Slider:slides'/* , array('grid-perPage' => $form->values->perpage, 'grid-paginator-page' => $form->values->page) */);
		}
	}
}