Lately I find that I see green stars on stories I’ve already seen listed in recent days. I think that problem had been fixed once before but it’s baaa-ack… 
The site uses your account and cookies to remember what you’ve already seen.
If you don’t log in and if you also disable cookies (like using Incognito mode or sth like that), this mechanic can’t work.
If both is not the case for you, then I’d need additional info what exactly is happening and how to reproduce it please…
Continuing the discussion from The green stars are misbehaving again:
I don’t log in each time because I seem to be permanently logged in. I go to User and it names me. I don’t think I block cookies. How can I find out in Mac Safari (Big Sur OS)?
I check in to the site daily. As of today, all stories starting on 3/25 still have green stars.