There was someone not too long ago that received a cooldown because they left their browser tab for Wayfarer on the Review page, and it kept timing out. They were working on other things, so they were bouncing around to different tabs without ending reviewing.
Niantic could possibly see staying on the Review page and timing out every 20 minutes as an abnormality with reviewing. You don’t want to stay on the Review page, so it’s best to go to another page on Wayfarer, like your profile or the showcase.