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All missed upvotes have been manually made up. Did you edit any previous posts before getting your upvote that day by chance? We have found that if someone edits a post prior to getting an upvote, the blockchain records that as a new post and the bot skips it for voting purposes...

Thanks for the tip @upex I had seen others discussing this matter too but since being with you I haven't edited any posts, so I'm not sure why the votes were missed, I feel it's more a Steem related issue because on those days some other usual votes also go missing or only appear much later.