Why does the router slow down before reconnecting?

Question

WiFi

The problem is this: on all devices, the network speed suddenly drops several times a day. It is treated by disconnecting devices from wi-fi and connecting back.

I tried: updating the firmware of the router and changing its settings, updating device drivers and system settings, changing the provider to another and replacing the router with a new one. Nothing helped.

The main question is why is this happening and how to get rid of it?

On the screenshots, measurements before and after reconnecting to the network

See screenshots

An important point is that over Ethernet, the speed is always stable.

Answer 1

Well, if you think logically, then when connected via Ethernet, it will always be stable, since it is directly connected to the modem.
What about WiFi? The more users, the lower the Internet speed for each. I had this on an old modem ( I don’t remember which model ), it was treated by buying a modern and powerful modem, instead of the old one. The problem is gone, how to drink to give. 5 years stable and without problems

Answer 2

Radio is radio. Don't expect miracles from him, especially in a noisy world :)