Sometimes 2.4g ssid disappear from wifi list

I've seperate 2.4 and 5g wifi's running. 5g is always visible but sometimes 2.4g is not visible at wifi list. when I turn off and on wifi 2.4 is visible again for a while. I could't find what triggers this?

any opinions?

What does dmesg have to say about it?

it's saying a lot of things. what should I lookiing for?