I'm loving the "Complete the Vocab" questions in the kanji quizzes, but unfortunately there's a bug that shows up from time to time.
Occasionally, two of the words to be completed require the same kanji (most recently it was 出題 and 出塁) but there's only one of the kanji I need available in the set of 4 that come with the question. So I either have to leave one of the words empty or drop the unused kanji in and get it wrong either way. it isn't super obtrusive, but it is still kind of a drag to have to get that question wrong.
I have no plans to let you duplicate, since it should not have that in the first place :). Next time it happens, can you please use the ? button at the top of the app/site, then "report a quiz error". That'll help me track it down :)