So I have a purchase flow including several forms. Each form is sent via Ajax to be validated, and if it is, the next form is returned and client-side code displays it. I have simplified the code (removed fields and some unrelevant control code) to the snippet below. My problem is: when Form1 validates through Ajax, Form2's template is returned …

page.php

public function form1() {
    // render template including Form1 form
}

public function Form1Form() {
		$f = BootstrapForm::create($this, "Form1",
			FieldList::create()
				->text('Name', _t('I18n.NAME', 'Name'))				
				->text('Address', _t('I18n.ADDRESS','Address'))
				->text('PostalCode', _t('I18n.POSTALCODE','Postal code'))
				->text('City', _t('I18n.CITY','City'))								
			, FieldList::create(				
				FormAction::create("confirmForm1", _t('I18n.YES','Confirm'))
			, RequiredFields::create("Name", "Address", "City", "PostalCode"));

		$data = Session::get("FormData.ConfirmForm");

		if(!$data) {
			$data = Member::currentUser();
		}
        $data->ID = $this->getOfferFromRequest()->ID;		
		$f->loadDataFrom($data);

		return $f;
	}



	public function confirmForm1($data, $form) 
	{
		Session::set("FormData.ConfirmForm", $data);

        // use form data

        // redirect to next form
		return $this->redirect($this->Link("form2"));
	}


	public function form2(SS_HTTPRequest $r) {
		// This function renders the second form, Form2, that shows the issue
        $order = $this->getOrder();
		i18n::set_locale($order->Language);

		$data = array(
			'Order' => $order,
			'Offer' => $order->Offer()
		);

		if(Director::is_ajax())
		{
            // custom header added for initialization purposes on the javascript side
			$this->getResponse()->addHeader('X-UpgradeOffer-Step', 'dealers');
            
            // Render the template for Form2 without any layout in case of Ajax request            
			return $this->customise($data)->renderWith('PurchasePage_form2');
		}
		else
		{
            // Let the framework render everything
			return $data;
		}
	}



	public function Form2Form() {
		$fields = FieldList::create();		
		$fields->push(HeaderField::create(_t('I18n.STEP2', 'Order step 2')));		
		
		$fields
            // FromDealer option with default to "N"
			->optionset('FromDealer', '', array('Y' => _t('I18n.BUY_FROM_DEALER', 'I want to order from a dealer'), 'N' => 'No'), 'N')
			
            // BuyDirectly option with default to "N"
			->optionset('BuyDirectly', '', array('Y' => _t('I18n.IWANTTOBUYDIRECTLY','I want to order online'), 'N' => 'No'), 'N')
            
            // Agree option with default to "N"
			->optionset('Agree',_t('I18n.DO_YOU_AGREE','I agree with sales terms'), 
				array(					
					'Y' => _t('I18n.YES','Yes'),
					'N' => _t('I18n.NO','No')
				),
				'N'
			);

		
		$submit = FormAction::create("confirmForm2", _t('I18n.NEXT','Next'));
		$submit->setDisabled(true);
		

		$f = BootstrapForm::create($this, "Form2Form", $fields, FieldList::create($submit));		

		// In both cases (ajax/direct load), $data is null when rendering the form for the first time
		if($data = Session::get("FormData.Form2Form")) {
			$f->loadDataFrom($data);
		}		

        // When DirectAllowed is false, the FromDealer optionsets always displays correctly, when
        // the BuyDirectly one stays incorrect (both radios checked when Ajax request)
		if(!$order->DirectAllowed)
		{
			$f->Fields()->dataFieldByName('FromDealer')->setValue('Y');			
			$f->Fields()->dataFieldByName('BuyDirectly')->addExtraClass('hide');
		}

		return $f;
	}