Phone stopps looking for messages after a time of inactivity
I have a strange issue with messengers like WhatsApp (official Android version and Mitakuuluu3) and Telegram (both Sailorgram and Jollagram).
It works well when chatting, I even get a ringtone when a new message arrives but if I stop using my phone for some time it seems to stop looking, although wireless is connected all the time (both wlan and sim as fallback). When I then send a message it seems to wake up and I get all the messages I missed during the hours of inactivity. Also works sometimes when I stop wlan and turn it back on after a few seconds, or switch to sim and go back to wlan.
Is there a setting I missed somewhere to tell the phone to keep looking for new messages all the time, or is this a bug?