Suddenly network reachable but no internet until reconnect manually

I had a similar problem although not quite the same. My wifi would go away. When I either reset the radio or went in and out of airplane mode it would work fine.

Then I realized if I ping’ed after about 10-20 seconds I would start getting replies and the wifi would work again.

What I discovered was power management for the radio was turned on and it was going to sleep. Sometimes it was easier to wake up than others.

If you run iwconfig it will tell you if power management is off/on. If you run iwconfig power off it will turn it off. On reboot it will reset to on. You have to change your config settings to make it permanent.

I haven’t had a radio/wifi issue since.