Shyvana stopping after using skill

I was playing Shyvana. In the first event i was targeting and attacking a champ with her ultimate, I was clicking on the champ but right after using her R I auto attacked the tower instead of attacking and pursuing the champion resulting in the tower killing me and the champion getting away. Another issue was after using her ultimate she stopped long enough to get snared or the tar beaten out of her, this also happened with her E. I had this occur multiple times in one game. I thought it was a lag but seemed only to happen a lot when using her ultimate.