Notify students - "NO" changing to "YES" -> Saving -> nothing saved

Hello 

Hope you can help me what am I doing wrong?

In spesific course we set the Notify students to "NO"

After the teacher go to "grade all submissions" and tick "Quick grading" change a grade and also then  change the "Notify students" to "YES" and click on"save all "quick saving changes" but nothing happen the"Notify students" still on "NO"

Why is that? Is it a bug?

Thanks

https://moodle.org/pluginfile.php/178/mod_forum/post/1254475/notyfy-no1.png