I was doing reviews and when I gave an answer for the meaning, it did the shake thing, but with no message. Because I’ve heard other people encounter this bug, I typed in the kunyomi even though it was asking for the meaning, and got a shake and message saying the onyomi was expected. So clearly it was expecting the reading even though it was asking for the meaning.
This happened multiple times in the same session, on various review items. Before the third instance, I turned off all user scripts. So it appears to be an issue with WaniKani itself, and not a script.
For what it’s worth, I had another tab open with a lesson session (the learning part, not the quiz part). I did about 15 review items, with this error occurring on and off, while the lesson tab was open. I then closed the lesson tab and refreshed the review tab, after which I completed the last 10 reviews without issue. I have no idea if this is related to the bug, but I wanted to mention it just in case.