I've think there's a bug with the daily challenges that involve doing X number of perfect quizzes, in that not all quizzes are counted toward the challenge. For example, today I had a challenge to do 3 perfect grammar quizzes. First I did my grammar schedule, which was too short to count, so then I did three 12 question verb conjugation quizzes, getting 100% on each. But I didn't get the challenge completion notification, and when I went to the dashboard it showed only 66/100% for the challenge completion. I though I must have missed a question, but my dashboard grammar stats said I correctly answered the last 66 questions in a row. I finally completed the challenge after doing a fourth perfect grammar quiz (also a 12 question verb conjugation quiz). This isn't the first time this has happened, though I'm not sure if it is consistent for all perfect quiz challenges, or restricted to certain quiz types or a specific number of quizzes needed. I only notice the bug when the challenge is for grammar or kanji, since those are the only ones I have to go out of my way to do additional quizzing to complete. I believe this has been happening since before the beta started, though I'm not 100% sure.