Hi Erel,
I think I have discovered the problem, i will try to explain it.
Some phone manufacturers(Nokia, Xiaomi, OnePlus,...), incorporate in their software an option to close applications in the background, related to the use of energy saving and ram. For this reason, when you block your phone, the services of some apps are stopped.
In my case, i am using a Xiaomi, and to solve the problem simply had to configure the app in "Background Configuration" mode as "No Restrictions".
Do you know if there is a possibility for to do this action automatically? or how to prevent this behavior of the app?
Excuse my poor English