Magento 2:An element with a “sellerpage” ID already exists

When i am making ajax call i am getting error ‘An element with a “sellerpage” ID already exists’.
Here is my controller.

namespace VendorModuleControllerSellers;

class Index extends MagentoFrameworkAppActionAction
{
    protected $_pageFactory;
    protected $resultJsonFactory;
    protected $_coreRegistry;
    public function __construct(
        MagentoFrameworkAppActionContext $context,
        MagentoFrameworkViewResultPageFactory $pageFactory,
        MagentoFrameworkRegistry $coreRegistry,
        MagentoFrameworkControllerResultJsonFactory $resultJsonFactory
        )
    {
        $this->_pageFactory = $pageFactory;
        $this->_coreRegistry = $coreRegistry;
        $this->resultJsonFactory = $resultJsonFactory;
        return parent::__construct($context);
    }

    public function execute()
    {

        $ajax = $this->getRequest()->getParam('isAjax');
        $id=$this->getRequest()->getParam('id');
        if($ajax == 'true')
        {
            try 
            {
                if($id)
                {
                    $this->_coreRegistry->register('id', $id);
                }
                $resultPage = $this->_pageFactory->create();
                $result = $this->resultJsonFactory->create();
                $block = $resultPage->getLayout()
                ->createBlock('VendorModuleBlockSellers')
                ->setTemplate('Vendor_Module::sellers.phtml')
                ->toHtml();
                $response['block']=$block;

                $result->setData(['output' => $response]);
                return $result;
            } catch (Exception $e) {
                $response = $e->getMessage();
                return $this->getResponse()->setBody($response);
            }
        }
        else
        {
            return $this->_pageFactory->create();
        }
    }
} 

here is my block

namespace VendorModuleBlock;
class Sellers extends MagentoFrameworkViewElementTemplate
{
    protected $_sellerCollection;
    protected $_storeManager;
    protected $_sellerList;
    protected $_coreRegistry;


    public function __construct(VendorModuleBlockSellers $_sellerList,VendorModuleModelResourceModelSellersCollectionFactory $sellerCollection,VendorModuleModelStatesFactory $states,MagentoStoreModelStoreManagerInterface $storeManager,MagentoFrameworkAppRequestHttp $request,MagentoFrameworkRegistry $coreRegistry,MagentoFrameworkViewElementTemplateContext $context,array $data = [])
    {
        parent::__construct($context, $data);
        $this->_sellerList = $_sellerList;
        $this->_sellerCollection = $sellerCollection;
        $this->_storeManager = $storeManager;
        $this->request = $request;
        $this->_coreRegistry = $coreRegistry;
    }

    protected function _prepareLayout()
    {
        parent::_prepareLayout();
        if($this->getRegSellerCollection())
        {

            $pager = $this->getLayout()->createBlock('MagentoThemeBlockHtmlPager','sellerpage')->setAvailableLimit(array(5=>5,10=>10,15=>15,20=>20));
            $pager->setShowPerPage(true);
            $pager->setCollection($this->getRegSellerCollection());
            $this->setChild('pager', $pager);
            $this->getRegSellerCollection()->load();
        }   

        return $this;
    }

    public function getRegSellerCollection()
    {
        $page = ($this->getRequest()->getParam('p')) ? $this->getRequest()->getParam('p') : 1;
        $pageSize = 5;

        if ($this->_coreRegistry->registry('id')) {
            $id = $this->_coreRegistry->registry('id');
            $collection = $this->_sellerCollection->create();
            $collection->addFieldToFilter('sellers',array('like'=>'%'.$id.'%'));
            $collection->setPageSize($pageSize);
            $collection->setCurPage($page);
        }
        else
        {
            $collection = $this->_sellerList->create();
            $collection->setPageSize($pageSize);
            $collection->setCurPage($page);
        }
        return $collection;
    }

    public function getPagerHtml()
    {
        return $this->getChildHtml('pager');
    }


}

When i am loading page it’s working fine. but whenever i am making ajax call it’s throwing error ‘An element with a “sellerpage” ID already exists’.