Apparently your bidbot does not take into account additional bids. I have sent 1 BEEM and then 3 more BEEMs to upvote post. But only the first transaction was accepted.
I would add that your bidbot votes every 2.5 hours. But every day, 20% of your SP is replenished. Change it to every 2.4 hours.
I sent 1 BEEM to promote a comment. And then I sent 3 more BEEMs to promote the same comment, but the second bid was not taken into account when upvoting. (I do not need that BEEMs, I just want to improve your service).