I've only ever seen this twice in the 1.5 years that I've been using the app. The sentence before this one in the recording (question 4) worked just fine. Question 5, didn't work for drag-and-drop. Tapping worked still. Once on question 6, dragging worked again.
In the video I have show touches turned on in Android debugging.
At the start of the clip you can see that tapping is still working. At the half-way mark I switch to dragging. Dragging didn't work at all for question 5, and only question 5.
