小程序 打卡  拍照上传，为啥偶尔会出现 黑图？

代码

  const ctx = wx.createCameraContext()

      ctx.takePhoto({

        quality: 'high', 

        success: (res) => {    

          wx.uploadFile({ 

            url: App.data.host_path + '********',

            filePath: res.tempImagePath,

            name: 'file',

            formData: {

              'rosterId': that.data.userid

            },

            success(res) {        

              let dares = JSON.parse(res.data)

              wx.hideLoading({

                complete: (res_hide) => {

                  console.log(dares.code)          

                  if (dares.code == '0000') {

                    wx.showModal({

                      title: '提示',

                      content: '签到成功',

                      confirmText: '查看',

                      cancelText: '不查看',

                      success: (res) => {

                        if (res.confirm) {

                        } else {

                          return

                        }

                      }

                    })

                  } else {

                    wx.showToast({

                      title: dares.msg,

                      icon: 'none',

                      duration: 2000

                    })

                  }

                },

              })

            },

            fail: (res) => {

              wx.hideLoading({

                complete: (res_hide) => {

                  wx.showToast({

                    title: '上传失败',

                    icon: 'none',

                    duration: 2000

                  })

                },

              })

            }

          })

        }

      })

代码 运行 没有异常

后台获取图片偶尔出现这种