ajax有时执行成功，有时报500错误

这是前台JS代码：

$(document).on('change','.figure',function(){



  var val = $(this).parent().prev().children().val();

  var value = $(this).val();

  

  var fh=$(this);

        

          $.ajax({

              url:"{{ path('detail_stock_ajax',{ 'icmoId':icmoId }) }}",

              type: "POST",

              data: {brandId:val,figureId:value},

              success:function(msg){

                

                fh.parent().parent().children('td').eq(12).empty();

                fh.parent().parent().children('td').eq(12).html(msg.stock);

            }

         })

       

     });

这是后台PHP代码

$brandId = $request->request->get('brandId');

        $figureId = $request->request->get('figureId');

        $brand = $this->getDoctrine()->getRepository('DianzibuyStoreroomDepartmentBundle:DzbStoreroomProductBrand')->findOneById($brandId)->getId();

        $products = $this->getDoctrine()->getRepository('DianzibuyStoreroomDepartmentBundle:DzbStoreroomProduct')->findByTitle($figureId);

        foreach($products as $value){

            if($value->getBrand()->getId() == $brand){

                

                $stock = $value->getStock();

                

            }

        }

        return new JsonResponse(array('stock' => $stock));

报错信息： Warning: rename(D:\phpStudy\WWW\Dianzibuy\var\cache\dev/doctrine/orm/Proxies\__CG__DianzibuyBundlePurchaseDepartmentBundleEntityDzbPurchaseSupplier.php.59bb801494e713.53833954,D:\phpStudy\WWW\Dianzibuy\var\cache\dev/doctrine/orm/Proxies\__CG__DianzibuyBundlePurchaseDepartmentBundleEntityDzbPurchaseSupplier.php):这里是乱码字符(code: 5)