I am having this exact same issue with one particular set of ActiveExpressions in our district. In several classrooms it works just fine - but in one room, I am experiencing the same exact problem you describe above. Note too that if I turn off the ActivExpression device and then turn it back on, the next question comes up, but then the same problem after that question is answered.
And this is with the same exact test being used in the different classrooms.
I hope somebody has an answer for this.