Greasy Fork is available in English.
Allows retyping typo'd answers, or marking wrong when WK's typo tolerance is too lax.
< Обсуждения Wanikani Double-Check
I am seeing this issue as well
Please post in the WaniKani forums Double-Check thread: https://community.wanikani.com/t/userscript-double-check-version-2x/31456
It's a lot easier to communicate there.
My first suggestion would be to make sure you have WaniKani Open Framework as the #1 script in TamperMonkey (or whatever script host you use). That's the only reason I'm aware of that it sometimes starts / sometimes not.
Script is disabled most of the time when I start reviews, I have to reload the page and turn on/off the script a couple times to get it working.