Dropping Wi-Fi signal on the router?

Question

Computer networks

The Wi-Fi signal on the router is constantly dropping.
That is, the Internet via Wi-Fi works fine, then it wildly slows down for 20-30 minutes.
After this time, it starts working normally again.
I thought the problem was in the router, I bought a new Zyxel Keenetic Extra, the problem remained.
The channel is set manually.
The wired internet works flawlessly.

Answer 1

router far from the client device? are there load-bearing walls, blinds, mirrors in the path, microwave ovens?

Answer 2

My opinion is that there are a lot of Wifi routers nearby and the signal is simply lost. Try changing the broadcast channel or play around with GHz. Should help.