I’m not sure what is the exact reason but both my messages sent to my friend and sometimes their messages tend to not show right after sending. I have to exit the app entirely and reload it for each and every message if I wish to keep the message history up to date which would like one of the two purposes of any messaging service; send messages and show them.
If it’s really a PITA to fix it I’d be happy with an in-app refresh button that just reloads conversation history.
I’m not sure about the scope of this bug, I definitely experience it in mobile app.