Do the test on the LG android 6 phone
The android app stops responding after about 5 hours..
If you leave the phone not used for about 5 hours
then send messages to the android phone you wil only set a black sent from the other phone.
Then you go to the phone that has been left for 5 hours and go into the app.
you can see the app says online
if you try to send meesage from the app you will only get the black sent too and no one will get your message..
if you kill the app and relaunch then app starts to function properly.. Messages that were sent before the app stop responding are lost.