Hello, again I am experiencing this problem. Some of the new terms to study shown before the vocab quiz then don't show up in the quiz. At the same time terms I have never seen before are showing up in the quiz. This always seems to happen, when I click the ignore button on potential new terms shown before the quiz. Just thought I would let you know again.
I figured as much. So, I was able to replicate the issue, apply a fix, and the issue disappeared for me (at least). Can you check and see if the problem persists for you?