system
13
My guess:
When you go to Run—Accessories—Notepad it does not link to the version of Notepad that you are thinking it does.
It is linking to another Notepad file.
This happens once in a while with Windows
Bottom line is that I think you have multiple versions of Notepad causing the problem because when you run it from wherever the icon is pointing to another directory. So you sandboxed one Notepad and when you went to run Notepad you thought you were running the version of Notepad that you sandboxed. However the Notepad icon that you ran Notepad from was linked to another version of Notepad that you did not sandbox, hence Notepad not running sandboxed when you thought it should.