Yes. While it wasn't quite without warning (we did send an email to all of our teachers) we understand that it was disruptive.
It was our intention to "lock" our courses for the school year, however, our data analysis was showing that some of our puzzles were producing severely lower understanding of concepts than what was expected. As such, we emailed all of our teachers and implemented an immediate refresh to make sure students received the quality of education that we strive to provide. These changes happened in all upper-elementary grades and resulted in an instant fix.
We do not anticipate another grand-scale update like this one during the 2017-2018 school year, though some individual puzzles might show small changes for clarification or enhanced learning.
We invite you to be a part of this continuing process by sending us reports on puzzles that you believe to have issues. We will work as hard as we can to get these issues resolved quickly!