Unseen words marked as learned/strengthened
Over in German, I was going through numbers again for practice, and at the end it said I had strengthened the word "Dreiviertel". It says I have seen the word three times, and have effectively mastered it, giving me all four segments on the mastery-o-meter (or whatever it is called :) ). I am absolutely sure that I did not see that word as I went through this section this time, and am pretty sure I have never seen that word in DuoLingo practice.
I was under the impression that other words have been incorrectly credited to me as having been seen several times and at least partially learned in the past, but was never quite sure. But I know that "Dreiviertel" is a word that was never presented to me.
I just noticed this as well. I just finished repeating a lesson and a word I never learned appeared as fully strengthened. I now notice that I have several of those words "learned"...
I'm pretty sure the word in question was in one of the "mark the correct translations" type of questions, but those questions shouldn't strengthen words that are not part of the correct translation!