In level 3 of the Russian course.
As usuall when you get a word/sentence wrong it goes to Difficult Words area. You work on it and that’s it. It only goes back to Difficult Words if you get it wrong again.
However there are 2 words, that once they go to Difficult Words you can never get rid of them!!! You can get the right answer 10 times and it will still be there. It never clears.
The two words are:
Кстати - by the way…
and
серьги - earrings
Very annoying bug because you have to repeat these words every single time you go to Difficult Words to practice words you actually need practice on!!!