During a particularly extensive research session earlier this week on one site I voted on 14 questions and 25 answers, and then I got the daily vote limit reached notice every time I tried to vote on another post of either type.
Via Email 201605251528510851 firstname.lastname@example.org confirmed the voting and said that if I was in fact getting the vote limit notice the rest of that day I should post it as a bug here. So here it is. Feel free to contact me for further info if needed to debug!
Wrzlprmft has it right. The first 25 votes for the day in question were composed of 17 answer votes and 8 question votes, giving a question-vote percentage of 32. In order to get the full 10 "bonus votes", you'd need at least 33.4%, so instead you only got 9 additional votes, putting you at a cap of 39 for the day.