Possible Bug in Malphite Ult + Hail of Blades

At 32:14 and again at 32:42 in the linked video, Anklespankin uses Malphite's Ult, followed by "W" and AA's. In both situations, there appear to be 3 attacks that entirely do not register damage. I've watched them each several times, and he does not appear to be animation canceling too early. I am unable to explain this in any way that makes sense, except to believe it's a bug. Can anyone confirm what is happening? Is this the proper way to report this?