Long delay before site is opened

I noticed that there is a long delay before site opens, sometimes it opens fast and sometimes it hangs for a couple of seconds. Never noticed this on my cellular connection. Any hints where to dig? Video attached
Wi-Fi: https://drive.google.com/open?id=1Ys0nw6WZJMvHUVSSvYHrduPw96M6HrlK - noticeable delay at 0:17
Cellular: https://drive.google.com/open?id=1Yn6xmO8j4GjOFnUwJdJXRectGziH9bML

Sites were taken randomly.

Router: Archer C7. OpenWRT 19.07.2

same here it's drive me crazy, i not sure why but the only solution i have found is to restart the radio from luci, can you confirm that doing that will make it work ok for like 2/3 howers?
this situation is in sta mode with ath9k.

Do you use adblock? For me it looks like delay in IP resolving.

no, plain openwrt , all default. this is happening on my ubiquiti powerbeam m2, that was a rock solid device fo years. it 's very strange the radio is connected but very high latency.

ok so this is the situation, the latency is very high, the download go to zero, upload is normal.
reverted to last LEDE and this is not happening. rock solid again.