If you are talking about the mail app on taskbar showing you mail you might have in numbers. I also sometimes have the issue that on the taskbar it still states one (or more) unread messages, but there are no unread messages in any of the accounts (one and one Gmail account). I had the same annoying bug, that eventually got worse in time (as soon as I opened my laptop the first notification froze restarting explorer stopped working as a faster way than restarting etc.).
Some may come with specific actions you can take. I will check the things you mentioned whenever the problem reoccurs. On the “Settings” dialog box, click the “System” icon. When you turn on the Game Mode feature, you will be able to use the Game bar to turn on Game Mode for each UWP and Win32 title you play.
