From update 5 if I am remember correct.
All day lay on the desk. This is all about it's background activity.
For example use
https://play.google.com/store/apps/details?id=com.uzumapps.wakelockdetector&hl=en , run the app, ansver positive when it asks you for root rights and keep it in background. Simple press Home button. In settings just confirm "Advanced Mode" and "Statistics from unplug".
Interface is very simple. You can switch between different type of wakelocks (Screen, CPU, Wakeup Triggers and Kernel Wakelock). We are interesting in this, Kernel wakelock only. I can see a lot of wlan_rx_wake and wlan_wd_wake here. Something in router prevent phones from deep sleep. Using "Enable WMM APSD" not helping at all. Flags that router distribute to this device are PSTAU, so the powersave mode should be enabled. Why the things going in that way they go I don't know.