As of late 2019, Quantum Country implements the following behavior; Orbit has always implemented this behavior. If you forget the answer to a question while reading an essay, the question will re-appear in the next review area in the essay (unless it’s the last review area, in which case it’ll reappear once you’ve answered all the questions in the current review area). If you forget the answer to a question while in a review session, it’ll reappear at the end of the review session.
This feature was roughly inspired by Anki’s “learning” queue. If I forget the answer to a prompt, then end my session early (i.e. before reviewing that prompt again), I feel that my memory of it is much less reliable. There is probably empirical data in the retrieval practice literature about this. I’ve not gone looking for it, and I haven’t yet stumbled upon it in my background reading.
Interestingly, the Spacing effect suggests that such rapid retry is unlikely to work as well as e.g. simply re-presenting the prompt in the next review session. But my instinct (and increasingly, our evidence) suggests that the retry intervention really does help. I haven’t yet read any literature on the spacing effect which separates out performance based on initial response success (though again, I imagine that such studies do exist).