You were almost there: the problem indeed comes from your inserting a second label inside a single Ibex-item array, which is an illegal syntax. Your code works perfectly well if you get rid of
"Question"—if your sentences and questions are paired, they represent a single item and so you shouldn’t need a second label.
You say that using
spr only wouldn’t account for the questions: what exactly are you trying to do? If you don’t want the Question controllers (when they exist) to be paired with a respective DashedSentence controller, you should simply called Template twice on your table, first to generate the DashedSentence items, and then to generate the Question ones.