I vote a lot on ServerFault: I've used up the maximum 40 votes per day almost every day for over a year, and for various reasons, I keep track of my voting, recording daily/weekly/monthly/quarterly/yearly/total votes every day.
A few months ago the rules were changed so that your vote count didn't change if you had voted on a question that was deleted. Prior to that, I had noticed my vote count "mysteriously" dropping by a vote or two every now and then.
But in the past two days, it's been happening again.
Today, I cast 41 votes (there's another - related? - glitch that sometimes allows you to vote more than 40 times per day), but my weekly/monthly/quarterly/yearly/all-time counts only went up 38.
Yesterday, I cast 40 votes and my weekly/monthly/quarterly counts went up by 40, but yearly and all-time counts only went up by 39.
It's obviously not a big deal, just a few votes here and there, but I'd like to know why it's happening when votes are supposed to count "forever" even if the question they were cast on goes away.