I think the probleem prolly lies to your introduction in the start.
the human brain always try to make assumptions based on its memory, for one that has a clear image of the cards he will automaticly assume your gimmick as a normal card the next time he sees it by recalling the image even if it is bloody obvious that it is a gimmick for someone else without the prior knowledge. this has been proven to be true for me many many times.
also alot of the subtleties that were used by wayne were not taught explicitly in the video but if you watch closely u will notice. when u are giving instructions to someone (which he conditioned them to do so from the starT).
it is difficult for them to also notice the gimmick, in fact there were so many subtle misdirection wayne used during his performance when he is showing the gimmick in the open.
I have used this effect numerous times and never did anyone notice the gimmick, but yeh moving it all the time prolly helps, although i found that to be abit weird.