This question already has an answer here:
After you try to vote on a post that was last edited X hours ago, you get the following message:
There is an unfair workaround - You can make a trivial edit to the post, then vote again on it.
While trivial edits shouldn't be encouraged, they still give you the ability to vote whenever you want on whatever you want, which can not fair sometimes.
Why it is designed that way? Shouldn't this be changed? I mean, shouldn't it be an error if you try to change your vote after editing someone's else post just because you want to change your vote?