I’m not sure if this is actually a bug or just a feature I don’t understand but I went to add a couple more fonts to my rotation and the number of vocabulary reviews I had afterwards increased significantly for all vocab schedules. My kanji and grammar schedules were not affected, which is what makes me think it might be a bug.
The fonts are wholly unrelated to anything inside the quiz engine, so there's no way it could affect it. Maybe something else in the settings panel? Check the settings under the Vocabulary section, and see if everything (especially the kanji knowledge stuff) is what you expect it to be.
It was extremely strange, I checked all my settings afterwards and they were normal. I went right from a quiz to settings, added the new fonts, then went to my dashboard and suddenly had a ton more reviews. The font had refreshed too but I don’t see how that could’ve been related. Anyways I’m not bothered by it so it was probably just a freak thing or maybe I did accidentally press something somewhere. Just wanted to report it just in case. Thank you for your reply!