https://www.youtube.com/watch?v=TDBB0vJg7WQ&feature=youtu.beNear the end of this video, you can see that when the thing is at 16 or 17 rock stacks and parrys to get 5 more rock stacks the timer doesn't restart on the 16th rock stack. Before the latest update when the thing had 16 rock stacks and parried to get 5 more the time for the 16th rock stack to go away resets. This is an annoying bug because if you had a 16th rock stack and parried and wanted to use a special 3 to get all the good benefits of having 20 rock stacks when using it you might only have 19 because the timer will take the 16th rock stack away.