If it's a single mistake or even two, I won't complain. Even HMX has made a good number of mistakes in their time. And their charting for a good handful of the RB1 disc songs is pretty questionable.
There's a good chance you own more "HMX DLC" than I do, but still. I'm not talking about "questionable charting" - it is very obvious that there's a glitched note in Cheval. Something that will abruptly throw off every single player, without question. I guess you could call it less of a "charting error" and more of a technical error. It's tough to explain, really, but it's not something I've ever seen Harmonix do.