Linksys WRT54G "loses" the network, what could be the reason?

Question

WiFi

The "dinosaur" Linksys WRT54G ver.7 fell into my hands. The task is very simple - through the WAN (dedicated network, DHCP) to distribute the Internet wirelessly to all home devices.
But bad luck - when the Internet is connected to the WAN port, a couple of minutes after turning on the router, all devices connected via Wi-Fi lose access to the Internet, and moreover, they cannot even ping the router.
There are many networks in the house - I tried to change the channel, the result is the same. Increased client lease time to "9999" - didn't help either. The network still falls off after a couple of minutes. You have to turn off / turn on the router, and then another couple of minutes is enough ...
The router itself does not heat up. The firmware is factory. Directly through the cable, the Internet works fine.
В какую сторону копать? Кто сталкивался с такой проблемой? Может ли тип шифрования Wi-Fi влиять на это?
Спасибо