1. Sometimes I quit the app by simply swiping the screen from the top, there isn't any message notification nor if I reopen the app, no new messages are shown

2. Then I quitted the app from the menu and reopened the app, then it would notify me there are a number of unread messages.

So, now, from time to time, I have to quit the app from the menu to make sure there isn't any new messages I missed.

I hope you understand what I mean.