Leblanc's Q not being mimicked

I was playing Leblanc today and I noticed that every time I would try to land a mimicked q combo, the second q would not go off. I trade this a few times by getting right in to the face of the other team just to test it, and it still would not work. Later I did the same combo on a creep and it worked just fine. I've never had this issue. Someone help!