All answers are marked as correct
I just did a strengthen skills for Norwegian and it didn't matter what I typed, it was marked as correct.
The first time it happened I missed a word out of a speaking exercise, then missed a letter off another word in the next question and by the end I tried typing random letters, all of which were accepted.
I've seen similar reports occasionally from other courses. So it's clearly a duo bug rather than a Norwegian course bug, although that was probably already obvious, since there's no "accept total nonsense" button which the incubator contributors, or their cats, could accidentally have pressed.
I've already interrogated my kitties.
They claim no involvement neither with this this, nor with the unfortunate 'knocking over a vase full of flowers while nobody else was in the house' incident. They've also assured me that the neighbour's dog is the one responsible for the muddy paw prints on our kitchen counter.