目前是只能单次上传，多次上传不行，请教一下问题出自哪？

js:
 //选择上传图片
 upload(){
  let that=this;
        wx.chooseImage({
            count: 4, //默认9
            sizeType: ['original', 'compressed'], //可以指定是原图还是压缩图，默认二者都有
            sourceType: ['album'], //从相册选择
            success: (res) => {
                if (this.data.wxzpsc.length != 0) {
                    this.setData({
                        wxzpsc: this.data.wxzpsc.concat(res.tempFilePaths)
                    })
                } else {
                    this.setData({
                        wxzpsc: res.tempFilePaths
                    })
                }
                that.addBtn(res.tempFilePaths[0]);
            }
        });
},
 //提交表单添加到数据库
 addBtn: function(e){
  let that=this;
  if(that.data.wxzpsc.length > 0){//1、判断是否有图片
    that.setData({
      //3、给上传图片初始化一个长度，上传成功的数组和已有的数组一致
      images_success:that.data.wxzpsc
    })
    that.uploadImage(0)//2、有图片时先上传第一张
    }
   
    
 },


 uploadImage:function(index){
  let that=this
    wx.cloud.uploadFile({//上传至微信云存储
      cloudPath:'wxzpsc/' + new Date().getTime() + "_" +  Math.floor(Math.random()*1000) + ".jpg",//使用时间戳加随机数给图片命名
      filePath:that.data.wxzpsc[index],// 本地文件路径
      success: res => {
        // 返回文件 ID
        console.log("上传成功",res.fileID)
        that.data.images_success[index] = res.fileID;
        that.data.images_success_size = that.data.images_success_size+1;


        if(that.data.images_success_size == that.data.wxzpsc.length){
          console.log("上传成功：", that.data.images_success)
        } else {
          that.uploadImage(index+1)
        }
      },
      fail: err =>{
        that.setData({
          images_success:[],
          images_success_size:0
        })
        wx.showToast({
          icon:'none',
          title: '上传失败，请重新上传',
        })
      }
    })


},