From other interactions it seems the people that run the site like feedback on bugs.

 

Here's a somewhat annoying one on CHP057.  On the final move I moved a pawn forward for what should be mate.  CM kept saying it was not the right move and to try another.  Nothing else seemed to give mate.  Finally I just asked for the solution and it was to move the pawn forward for mate.  Heh heh, I felt pretty smart that I did get the right answer but someone who cared that they had kept getting penelalized trying the same move might.

Ok, thank you for reporting this. We are working to correct this lesson.

Ok, this lesson has been fixed.