I have a related but different experience: it's constantly asking me about "library" or "spring" and it's been a long long time since I've made a mistake. Why i

I have a related but different experience: it's constantly asking me about "library" or "spring" and it's been a long long time since I've made a mistake. Why is it not trying to review other words where I do make mistakes, or even words where I need to click on the translation / listen to the audio multiple times? It always makes me a little doubtful of their claims.