The font in TextEdit does not change as expected after attempting to modify it

Steps to reproduce the issue:

open example program "textEdit" under the directory qtbase\examples\widgets/richtext\textedit

When you load example.html in the editor and change the font of the first paragraph from Arial to System, then save the file as example1.html, reloading example1.html and attempting to change the first paragraph back to Arial will not work.