I noticed this a little bit ago on an older question. I clicked "vote to close", but the box that came up said, "You cannot vote to close again after retracting your vote." I figured I just had change of heart in the past and had retracted my close vote.
But then I was looking at more recent instances of questions I have voted to close that were closed and then reopened. If I click to vote to close I still get the same message: "You cannot vote to close again after retracting your vote," even though I never retracted a close vote.
Functionally, I suppose this doesn't make a difference. But I just wanted to raise the issue. I think the message used to say something like "you have already voted to close this question" or something like that.