I was making the voting rounds just now when I ran into a strange issue. I've noticed since HF 19 that sometimes posts would disappear and reappear after refreshing Home a few minutes apart. Perhaps more worrisome, though, I've also noticed that posts I was sure I've upvoted have lost my little blue up arrow 
!!
I thought maybe I was just going crazy. Or maybe my upvote never connected to the server. This is reasonable, since the website and blockchain are getting slammed with activity after HF 19.
Finally I have incontrovertible proof of a bug!
Over the past half hour, I came across a post I thought was a good one:
So naturally, I upvoted it:
Not more than half an hour later, I was browsing new posts again, and lo-and-behold the post I remember liking so much showed no signs of being upvoted by me. My natural reaction was to rectify the situation by upvoting it correctly this time:
Finally, I refreshed the page again and was satisfied the white up arrow had turned blue.
Nevertheless, something didn't sit right with me. I was sure I'd upvoted it properly on my first attempt.
Rather than go through the trouble of manually parsing the blockchain, I used steemd.com for convenience to lay out my recent vote history. What did I find? No other than the proof shown above, that two separate transactions contain my votes for the post listed above. Here is the transaction history laid out reverse-chronologically:
So there you have it; a post I was able to upvote twice! And with differing weights no less!
What could have happened here? Is steemd.com perhaps wrong? Was my first vote invalidated?
I'm hoping a dev or someone with more knowledge of the Steem inner-workings is able to answer these questions.
Hi,
When you double vote on a post, your second vote cancels your first one.
Both votes are registered on the blockchain but only the last one is valid. Your curation rewards are 0℅ and your vote worth $0 for the author.
Here, look:
Oh, ok, i commented before reading the other comments, my bad. Well then, but you VP is still spent, isn't it?
Yes, VP is spent for this transaction, and your VP also decreases when you reverse your vote (upvote to downvote or back) but no extra VP spent for cancelling.
I get the point, that only makes you more careful with your actions.
I think that's right. I've seen this happened. Now when I vote for something and my bot passes after me, the second vote gets in to cancel my first vote. It didn't use to be the case. The bot used to skip a post I already had voted on.
I'm not sure how it happened for you that you were able to cancel your other vote without actually cancelling it but that seems to be what happened.
Yep, @neander-squirrel is absolutely correct. There was definitely a display issue as to not show the previous vote on Steemit.com, and the second vote overwrote the first.
Interestingly, if the vote power was identical, the second transaction would fail :)
Followed! UV this comment also, great job by you, I am not a big tech guy
LOL!!!
I have the same problem and I am mainly using my smartphone and ipad for viewing posts.
Me too. It's happened to me a few times on mobile and through esteem as well and I was wondering what was up.
I guess quite a lot of people have this problem.I have encountered this problem when using my smartphone (using chrome as browser) and ipad(safari). Quite shocked that esteem has this problem also. We need to be careful that not to cancel our vote and waste the precious voting power by mistake. I hope this problem would me fixed soon.
Hi @geoffrey,
Can you give me a link to the post please?
The post I upvoted twice accidentally? Sure!
https://steemit.com/bitcoin/@kingscrown/interesting-bitcoin-news-today-electrum-bitpay-blockchain-info-kraken
Speaking of your upvotes, I just wanted to thank you for your upvote of my post today -- this one -- you were a big part of the push to get me a really nice payout on that post, which moves the needle for me on my goals here on steem and in general for me income-wise, so thank you again! Now following.
I think I have had a feeling something was wrong with some of my votes in the past but I didn't give it much thought then. Good find and thanks!
I think that is right. I've seen this happened. currently once I vote for one thing and my larva passes once Maine, the second vote gets in to cancel my 1st vote. It did not use to be the case. The larva accustomed skip a post I already had voted on.
I'm undecided however it happened for you that you simply were ready to cancel your alternative vote while not truly cancelling it however that appears to be what happened.
Hi
Can anybody let me know what's with the figure in circle, like 25, 59, 72.......?
That's the author's reputation. Upvotes bring it up, and downvotes bring it down. It's on a log scale. Here's more info on it.
Thanks, upvoted again
seems like a pretty big problem.
@ned @dan @timcliff please review this
dan is no longer part of steemit. If anyone should be taking a look at this is @sneak the current lead developer.
o wow, I didn't know that! thanks
Ya, neither did I. Hmmm. No worries, it was still his baby.
I think this more a UI issue. Steemd.com clearly shows that your first vote was recorded on the blockchain.
Normally steemit.com says "You already voted in a similar way" when I try to upvote a post that the website "forgot" about. This is the only time I caught it let me actually upvote a post that my browser isn't aware I already upvoted.
That's why I think it's a user interface issue with steemit.com. I have voted twice on the same post before by mistake but using other interfaces other than steemit.com
Ah okay, gotcha. Thanks!
wow good find and glad that my post was the one helping you to find it :) again i did something good for STEEM :)
I have noticed a small handful of other sharp users saying similar things incl, one who has commented in this post and I was chatting by PM with!
Great find and thanks for taking time to write this up so well @geoffrey!!
Hello @geoffrey, I feel you. Happened some time where I voted, refreshed page, vote gone, voted again, refreshed page, vote gone. Usually at the 3rd time it appears.
Another problem I encounter is with the comments. I write them, press post and they don't appear on the page and it is not saved in drafts. Since then I copy paste the text from a word file and doublecheck it if it has been posted.
That is alarming. Glad you notice. I hope the fix the bugs soon! It was strange, because yesterday I made a post... I swear I pressed post... I saw it briefly and then the whole post disappeared all together. I ended up just redoing the post and submitting it... but I thought that was strange.
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I think it is a display error. I have noticed that some posts that I have already voted on don't show a vote. Then I go to vote and it says I have already voted.
good post
@geoffrey thank you for voting for me as a witness! I will continue voting for you as a witness as soon as you get updated to the current version and get the pricefeed current as well!
That is weird, never encountered that before, or.. did not notice. In the essence is just against everything that blockhain represents. Did it also give the rewards form the reward pool to the author after up voting multiple times? Bu since the block size is 3 seconds... it might theoretically happen that both upvotes were included in different blocks as separate transactions. That should be a front end issue then.
A witness only include a transaction if he have consensus with other nodes who also have copy of the blockchain.
Double vote is like double spending. Not possible on any blockchain unless compromising the nodes.
I'm not worried about double spend then. Thank you for your elaboration on the topic.
Yes, Some time it happens me too !
I just read this and thought it was recently...phew