OK so I noticed something I haven't before, the app seem to be now affected by the phone's screen sleep timer.
I remember in previous versions I can go downstairs and grab a snack and come back with the game still on and my character on AFK. Like when you have a video running on Youtube, the phone won't sleep. Now I just peeked out a window and found the screen off. My sleep timer is 30s.
I also found that if I have the battle screen active, when I wake up the phone all the buttons become unresponsive (even the options button). The chat usually stays active for a bit longer, long enough to see the "you are now afk" message pop out though I can't chat.
I haven't tried multiple test but when I just parked my character and waited for the phone to sleep then woke it up, it seemed to function normally.
Guess I'll just have to change the timer setting whenever I play PRO. This is not as bad in previous versions where I automatically get logged out when I switch to a different app even for just a few seconds.