Maybe you're trying to pull it off too fast? keep everything smooth. Usually, I do this as a closer to the ambitious card and at that point, most are like "how/why is that happening?" My patter at that point is usually, "Look, alright, I'll do this as faily as possible. Just watch the card go in the whole time (just don't emphasize the word watch)." I close the fan in a flourishy way and hit the top of the deck, usually, they're so confused, looking at the deck, that they'll eventually look at you. Like I said, don't go too fast, spectators, especially intuitive spectators, will be able to sense when you move, so draw them in. I hope that helped a little...