Where is this text coming from at the end of my checkout URL?

I’m adding a “buy now” button to my site. I’m using the code from here.

When I click the button, my site tries to go to example.com/checkout/#93=4, which then results in it going to example.com/checkout/noroute. Where is the #93=4 part coming from? I’ve tried to step through the Magento code in a debugger, and as far as I can tell, the extension is trying to go to example.com/checkout/, and I can’t figure out what’s adding the #93=4. But I’ll be honest; I don’t understand Magento’s routing.

Here are the parts of the code that I think are relevant:

buynow.js

define([     'jquery' ], function ($  ) {     "use strict";     return function (config, element) {         $  (element).click(function () {             var form = $  (config.form);             var baseUrl = form.attr('action'),             buyNowUrl = baseUrl.replace('checkout/cart/add', 'buynow/cart/add');             form.attr('action', buyNowUrl);             form.trigger('submit');             form.attr('action', baseUrl);             return false;         });     } }); 

Add.php

I’ve used the debugger to verify that the line $ baseUrl = $ this->_objectManager->get('\Magento\Store\Model\StoreManagerInterface')->getStore()->getBaseUrl(); towards the bottom of the code does return example.com/checkout/ (no #93=4)

class Add extends \Magento\Checkout\Controller\Cart\Add {     /**      * Add product to shopping cart action      *      * @return \Magento\Framework\Controller\Result\Redirect      * @SuppressWarnings(PHPMD.CyclomaticComplexity)      */     public function execute()     {         if (!$  this->_formKeyValidator->validate($  this->getRequest())) {             return $  this->resultRedirectFactory->create()->setPath('*/*/');         }          $  params = $  this->getRequest()->getParams();         try {             if (isset($  params['qty'])) {                 $  filter = new \Zend_Filter_LocalizedToNormalized(                     ['locale' => $  this->_objectManager->get('Magento\Framework\Locale\ResolverInterface')->getLocale()]                 );                 $  params['qty'] = $  filter->filter($  params['qty']);             }              $  product = $  this->_initProduct();             $  related = $  this->getRequest()->getParam('related_product');              if (!$  product) {                 return $  this->goBack();             }              $  cartProducts = $  this->_objectManager->create('Test\BuyNowButton2\Helper\Data')                              ->getConfig('buynow/general/keep_cart_products');             if (!$  cartProducts) {                 $  this->cart->truncate(); //remove all products from cart             }               $  this->cart->addProduct($  product, $  params);             if (!empty($  related)) {                 $  this->cart->addProductsByIds(explode(',', $  related));             }              $  this->cart->save();             $  this->_eventManager->dispatch(                 'checkout_cart_add_product_complete',                 ['product' => $  product, 'request' => $  this->getRequest(), 'response' => $  this->getResponse()]             );              if (!$  this->_checkoutSession->getNoCartRedirect(true)) {                 $  baseUrl = $  this->_objectManager->get('\Magento\Store\Model\StoreManagerInterface')                             ->getStore()->getBaseUrl();                 return $  this->goBack($  baseUrl.'checkout/', $  product);             }         } catch (\Exception $  e) {             // ...         }     } }