You can not image what I've found!
I had a lot of time to find out what is the problem with my router.
Earlier there was an event, my child somehow pushed down the router from the shelf with a small ball when they played in the room.
The central antenna, at the connection part was broken, but when I checked it first time after the accident I couldn't identified.
Somehow I've checked it again, when we cleaned up the room. And two parts was in my hands. A router with a metal connector and the 3rd antenna. Hmmm. I've replaced it.
Finally working right, and everything is fine again!