wx.openDocument打开pdf没有反应？【求解官方】

wx.downloadFile({
          url: FileName,
          filePath: cachePath + `/${AgreementName}`,
          success: function (res) {
            if (res.statusCode === 200) {
              wx.openDocument({
                fileType: "pdf",
                filePath: cachePath + `/${AgreementName}`,
                success: function (res) {
                  console.log('打开PDF成功');
                },
                fail() {
                  wx.showToast({
                    title: '打开文件失败',
                    icon: 'none',
                    duration: 3000
                  })
                }
              })
            }
          },
          fail: function (res) {
            wx.showToast({
              title: '缓存文件失败',
              icon: 'none',
              duration: 3000
            })
          }
        })
iphone xs max并不是偶现，每次都走了wx.openDocument成功的回调，但就是不显示pdf文件。。。不显示的频率远大于出现的频率，看这个问题社区已经出现可很久了。