Blank content in a saved Windows Notebook file

The written stuffs in a Windows日记本(diary) file dissappeared when be opened again. I saved it but esp. after saved more than 2 times during the edit, the files may become blank. I use the bluetooth pen to write on a file.

用Windows笔记本手写记录文件，保存后，再打开，文件变成空白。尤其是编辑过程中，二次保存后，都是这样。比较纠结。

希望得到帮助。