Notifications don't show up until I wake the phone

[AC Question]

Hi, I have identical problem on two Nexus 5x phones.
In last few weeks I've noticed that I don't receive any notification(Gmail, calendar, sms...) when phone is in "sleep mode" but when I wake it up (with power button, shake etc) the notifications show up immediately.

1. I thought there is something wrong with the notifications settings:
Settings->notifications->configuration:
- Pulse notification light: "ON"
- On the lock screen: "Show all notification content"

2. I checked every settings of every app - everything is set correctly

3. Battery saver - "OFF"
Settings->Battery->Battery saver

4. Doze (battery optimization for apps)
Settings->Battery->(drop down menu)->Battery optimization
Every app moved to "Not optimized"

and still...NOTHING

Technical info:
Phone: LG Nexus 5x
OS: Android 7.0 (Nougat)
Rooted: NO
Custom ROM: NO
Connection: tried with every combination = Offline, WiFi, Mobile data, Wifi + data

Thx for help and sorry for my english

 

[the tall guy]

Hi, do you have "do not disturb" enabled on the phone?

 

[Jarda Jakoube]

Hi, thx for reply.
No. The "Do not disturb" is disabled.