前端代码如下，为什么一调用getLocCode页面就报错，但是看接口是返回成功的？

ajax请求失败，状态码： 200 ,状态: 4 ,错误信息: parsererror

  const getPDFData = () =>
    new Promise((resolve, reject) => {
      fetchData(_this, options, function (res) {
        resolve(res);
      });
    });

  let res = await getPDFData();
  //获取库位
  let barcode = res.data.records[0].barcode
  let optionLoc = {
    url: `/wmsrest/product/outwx/getLocCode?sn=${barcode}`,
    type: "post",
    // condition: parameter,
    contentType: "application/json; charset=utf-8",
  };
  const getLocCode = () =>
    new Promise((resolve, reject) => {
      fetchData(_this, optionLoc, function (res) {
        resolve(res);
      });
    });
  let locCode = await getLocCode();