@Kumirei I did some refactoring for WK Item Info Injector, and also adapted it to work with the recent change of the lesson notes to React. Can you update the @require to use the newest version?
// @require https://greasyfork.org/scripts/430565-wanikani-item-info-injector/code/WaniKani%20Item%20Info%20Injector.user.js?version=972944
Sorry if this starts to be annoying. I expect that the next breaking change due to the ongoing transition to React will come pretty soon.