Why does the Internet disappear on the router for several hours?

Question

Computer networks

Hello, such a problem - the Internet disappears through the router, rebooting the router does not help, the cable sees, there is no network. The Internet disappears for different periods of time, from 15 minutes to 5-6 hours, if connected directly to a computer, then everything works, the problem appears chaotically, either day after day, or disappears for a month.
What could be the problem?
Equipment - Zyxel Keenetic Start.

Answer 1

Also, if possible, change the wan port of the router to another, obviously working one.