从低版本（3.9.7）升级到3.9.11，保存图片到相册没问题。

之后卸载微信，不保留数据，重新安装，再次下载多图会导致闪退。

保存到相册代码如下：

// 去掉图片链接所带参数  
getOriginImgUrl(url) {
    return url.split('?')[0];
  },
  getPhotosAlbumAuthorize() {
    return new Promise((resolve, reject) => {
      wx.getSetting({
        success: (res) => {
          //检查是否有访问相册的权限，如果没有则通过wx.authorize方法授权
          if (!res.authSetting['scope.writePhotosAlbum']) {
            console.log('没有获取授权');
            wx.authorize({
              scope: 'scope.writePhotosAlbum',
              success: () => {
                //用户点击允许获取相册信息后进入下载保存逻辑
                resolve();
              },
              fail() {
                reject();
                wx.showModal({
                  title: '未获取相册授权',
                  content: '请点击右上角胶囊按钮，打开设置，将相册权限打开',
                  confirmText: '确定',
                  showCancel: false
                });
              }
            });
          } else {
            console.log('已获取授权');
            resolve();
          }
        }
      });
    });
  },
  handleDownload() {
    this.getPhotosAlbumAuthorize().then(() => {
      this.sequenceDownload();
    }).catch(() => {});
  },
  sequenceDownload() {
    const filesUrl = this.data.banners.map(url => {
      return this.getOriginImgUrl(url);
    });
    const proInfo = this.data.detail.description;
    if (filesUrl.length) {
      wx.showLoading({
        title: '下载中',
      });
      const allPromises = filesUrl.map(url => this.downloadFile(url));
      Promise.all(allPromises).then(() => {
        wx.hideLoading({
          noConflict: true
        });
        // 复制商品描述到剪切板
        wx.setClipboardData({
          data: proInfo,
          success () {}
        });
        //保存成功弹出提示，告知一下用户
        wx.showModal({
          title: '提示',
          content: '已保存到相册，商品描述已经复制到剪切板',
          confirmColor: '#E0B77A',
          confirmText: '知道了',
          showCancel: false
        });
      }).catch(err => {
        wx.hideLoading({
          noConflict: true
        });
        console.log(err);
        wx.showToast({
          icon: 'none',
          title: '下载保存失败，请重试'
        });
      });
    }
  },
  getFileName(url) {
    const splitArr = url.split('/');
    return splitArr[splitArr.length - 1];
  },
  downloadFile(url) {
    return new Promise((resolve, reject) => {
      wx.downloadFile({
        url: url,
        success: (res) => {
          var savePath = wx.env.USER_DATA_PATH + '/' + this.getFileName(url);
          const fs = wx.getFileSystemManager();
          fs.saveFile({ //下载成功后保存到本地
            tempFilePath: res.tempFilePath,
            filePath: savePath,
            success() {
              //获取了相册的访问权限，使用 wx.saveImageToPhotosAlbum 将图片保存到相册中
              wx.saveImageToPhotosAlbum({
                filePath: savePath,
                success: () => {
                  resolve();
                  // 保存完成后删除本地缓存文件
                  fs.unlink({
                    filePath: savePath,
                    fail(errmsg) {
                      console.log('remove file fail:', errmsg);
                    }
                  });
                },
                fail(err) {
                  reject(err);
                }
              });
            },
            fail(err2) {
              reject(err2);
            }
          });
        },
        fail: (err) => {
          console.log('download error', err);
          reject(err);
        }
      });
    });
  },