In tundra, sometimes (occasionally, not regularly), after reaching the green portal, I am able to use it after leaving the portal field itself as well.

(I reach the green portal, the green portal icon lights up, then I leave the portal field and the portal icon is still green.)

Such usage transports me nowhere. Using the green portal without being on the portal field will only generate a page with Beastkeeper background. (with logo, game title and the green-brown wallpaper)

Thank you for reporting. We tested the described issue and found out that the portal icon changed the visual state on the movement animation end, while  the actual state was changed on the animation start. So there really was a small time when clicking it took you to a blank page. This didn't do any harm to a pet, and exploring could be continued after page refresh, but a blank page could look really confusing. We updated the logic so now there's no time gap between change on the frontend and the backend. Sorry for the inconvenience.