Upvote should not change to downvote after some “X” hours (like 48 hours)

I was practicing for the “Curator” badge – Read the items of others, and suddenly I noticed that this should be a feature of the website from the start of the website.

Originally, it had 1 Vote. I clicked for “Upvote,” and the count went to zero. It means there is a clear UI issue that I can’t identify that I already upvoted here.

And Upvote must not change to downvote after X hours, like 48 to 72 hours. Otherwise, one day I will add upvotes to the Roadmap, and by mistake, on other days I will remove my upvotes. At last, I can’t be eligible for the “Curator” badge, and I can’t stand with my decisions either!