for grammer quizzes , randomize quiz order doesnt seem to work. i let grammar build up for a few days, and when i do the quiz, questions get heavily clustered still. noticed several times and now i do think it's a bug.
Do you have this turned on? Maybe the order of the grammar expressions themselves is randomised, but the questions stay clustered? "Randomize Study Order" seems to shuffle "ready to review" terms, and for grammar that refers to the expression, not the questions associated with it.