Kanji schedule 8135 has a double cache mismatch with two terms that are unable to be studied. Clicking the start quiz button just causes Kao to shake her maracas indefinitely. With flushing now completely deprecated, there's no way to fix.
I think it's related to the removal of much of the information in the kanji dictionary and the mismatch between what is seen in quizzes and what is shown in the dictionary.
Flushing actually still works, ?flush on the end of url.
That being said, I am in the middle of a major kanji reading (largely rare readings) update as we finally got access to a commercial level dataset for kanji (which I haven't yet announced), and the readings are being adjusted to match that.